In April 2011, Mdsuhair asked a question at the Chandoo.org Forums
This is a candidate for Solver.
This post will walk us through the solution to the problem using Solver. It uses Solver and screen shots from Excel 2007.
All versions of Excel have solver available. Users should note that the screen shots may not match your version although the functionality will, some of the functions appear in different locations in different versions of Solver.
What and Where Is Solver
What is Solver
Solver is an Excel add-in that can solve problems by enabling a Target cell to achieve some goal.
This goal may be to minimse, maximise, or achieve some target value.
It solves the problem by adjusting a number of input cells according to a set of criteria or constraints which are defined by the user.
Where is Solver
Solver is an Excel add-in supplied with Excel, but not enabled by default.
To enable solver
File, Excel Options, Add-ins, Manage Excel Add-ins, Select the Solver Add-in checkbox
Solver will now appear as a New Tab on the Data, Analysis Tab
Solver Example
This post is based around a worked example Solver Example File, the file is compatible with all versions of Excel.
Defining the Problem
Mdsuhair had a series of 8 Items each which had a value:
He wants to know which items should be combined so that the sum of the values of the items is nearly equal.
To do this we need to assign each item into a Bucket. Namely Bucket A and Bucket B.
We will put values of 1 into a Bucket for each Item to show that it is assigned to that Bucket and a value of 0 to show that the bucket is empty (In/Out) Value.
We can start by adding a Total Column, which counts items in Buckets A + Bucket B for each Item, It then totals the totals.
We also know that we need to work out the Value of each Item in each Bucket
We do this by multiplying the Items Value by the Buckets (In/Out) value
Finally we need to add up the values in each Bucket and work out the difference between them
Mdsuhair’s original problem was to minimise the difference between the sum of the values in the 2 buckets.
Now we can place values of 1 in the buckets manually and Excel will show us the value of each Bucket and the Difference between them in Cell G11.
I have applied some conditional formatting to show when a cell has a value > 0.
The problem is that there are 28 or 256 combinations of answers, and to test them all manually at 1 every 5 seconds would take 21.3 minutes, assuming we can keep up that pace and remember which was the best combination.
This is where solver comes to the fore.
Applying Solver
To apply solver we need to define a series of requirements, rules and constraints.
These requirements, rules and constraints guide solver and set limits which allow solver to quickly narrow in on the answer.
What are our rules
Our main requirement is to minimise the difference between the value of the 2 buckets.
The difference between the 2 buckets in our example is cell G11, the sum of Bucket 2 values minus the Sum of Bucket 1 values.
We want to have G11 as low as possible but greater than or equal to 0.
We also know that an item can only be in Bucket A or Bucket B, it can’t be in both and can’t be Broken apart.
That is 2 Constraints for each Item
Firstly The Total column must be equal to 1
Secondly the Buckets Values must be Integers
We also know that the Total Number of Items is 8, this is another constraint.
We will discuss how these constraints are used in the next section
The Solver Window
This section will explain the solver window and its use in defining the problem within solver.
A Blank Solver Window
A Filled Solver Window
Set Target Cell:
This is the Target cell which is the cell which you are trying to solve the problem for.
Our Target cell is G11, The difference between the 2 Buckets values
Equal To:
The Equal To: section defines what we want to do with our Target Cell.
We want to achieve the same value in each Bucket and so the difference between the Buckets will be 0.
It might sound strange but we don’t want to minimise that difference. A minimal value will be achieved when all the Items are placed in Bucket A, as our equation for G11 will then have 0 – Total which is –Total, which is more minimal than 0.
Another way to constrain this is to Change G11 to =Abs(G10-H10)
This allows us to use Min as an Equal To: Value
But for now we can just leave G11 as =G10-H10 and we will set the Equal To: section as 0.
By Changing Cells:
Changing Cells: refers to the cells which will be modified by Solver to try and solve the problem.
We want to let Solver change the number of items in each bucket, this is the range: $C$2:$D$9
Hint: You can try the Guess button next to the Range Reference and Solver will take a Guess at what cells the problem is dependent on.
Always check this if you use it, especially in complex models.
Subject to the Constraints:
Constraints are the rules which define the limits of the possible solutions to the problem
We will add several constraints for our rules:
1. The Total column must be equal to 1 for each Item
2. The Bucket Value must be an Integer
3. The total contents of the 2 buckets must be 8 items
4. You could add a further constraint that each Bucket should hold the same number of items
Hint: As a general Rule, Under Constrain rather than over constrain! You can always add more constraints later.
To do this we will use the Add Constraint Button
1. We need to add a constraint for each cell in the Range E2:E9 that it is only allowed to be = 1
This constraint must be applied for each cell in the range E2:E9
2. We need to add a constraint for each cell in the Range C2:D9 that it is only allowed to be an integer
This constraint must be applied for each cell in the range C2:D9
3. We need to add a constraint for the Total of the 2 Buckets, E10=8
You can Change or Delete Constraints if you make a mistake by selecting the appropriate constraint and using the Change or Delete Buttons
Save and Load Solves Parameters
Selecting the Options Button there is the Option to Save Model and Load Models.
Hint: The Save/Load Models has been shifted onto the main Solver dialog in Excel 2010.
Using the Save Model and Load Model options you can Save and the Load the Solver Parameters for your model. The Save Model saves the parameters in a Range of cells as shown below.
This allows an easy way to actually setup and/or change the solver parameters.
Hint: Setup one constraint using solver then Save the model. Edit the model on the worksheet and re-load the model as required.
Note: That the parameters although when saved show as True/False or Numbers are all Excel Equations, see above.
This means you can edit them to change the Constraints and Parameters as required and re-load them into solver.
I have included 3 sets of Parameters for our model.
These are:
- Base Case – Forces bucket values to be equal, Allows uneven bucket counts
- Equal Sized Buckets – Forces each bucket to contain the same number of items
- Force an error – Which forces an error in the solver model
Load each model and try them at your leisure.
Running the Solver Model
Warning: Solver is a computationally complex add-in, so once your model is setup, Save your Workbook.
Prior to running the model there are a few parameters we should look at to ensure the model solves correctly.
On the main Solver window select the Options button. (Some of these parameters are on the Main Solver window in Solver 2010)
Generally you can accept the defaults but in this case we will change the following
Assume Linear Model – Select
Assume Non-Negative – Select
Note: Solver in Excel 2010 will return a better answer without these 2 parameters enabled by default
The other 2 parameters which you may need to change from time to time is
Precision: Precision is a number from 0 to 1 and higher means more precise
Tolerance: Tolerance shows how far away from a Number, an Integer constraint is allowed to be
The use of the Estimates, Derivatives and Search parameters are beyond the scope of this post. I direct you to the Excel Help on these subjects, by selecting the Help button.
Run the Model
To Run the Model, select the Solve Button from the main Solver menu.
The main status bar in Excel will flash up a number of statistics about the internal workings of the Solver add-in. Generally these flash by and are too fast to read. If a model is too complex it may stall and you won’t see any movement for a while. Solver generally recovers from these problems itself.
Once the Solver model finishes it will display a dialog of the results and allow you to do several things
First thing to note is that “Solver Found a Solution“.
If it has found a solution, the worksheet cells will be changed to show the solution
You now have 4 options:
- Run a Report
- Save a Scenario
- Return to the model
- Check Your Results
Run a Report
Run a report by clicking the report you want.
A new sheet will be added to your workbook depending on the report but will be called:
- Answer Report 1,
- Sensitivity Report 1
- Limits Reports 1
etc.
Note, that not all reports are relevant at all times, depending on the Constraints you have applied.
Save a Scenario
Selecting the Save a Scenario button takes you to the Save Scenario dialog.
Type in a Name and the Scenario of your model is saved as a Scenario.
Scenarios as available for use in the Scenario Manager, which is accessed from the Data, What-If-Analysis Tab
Return to the model
You can return to your model and either:
- Keep Solver Solution
- Restore Original Values
Check the Results
Solver is probably the most Black Box’ish of systems within Excel. As such any results it puts out must be manually checked for suitableness before further use.
These checks for realness, should as a start confirm that the results meet all the criteria supplied.
Are the results roughly what were expected?
Are any Minimums or Maximums violated?
What If Solver Doesn’t Find a Solution?
From time to time Solver will return with an error that a “Solver could not find a feasible solution.”
When this happens it is indicating one of several possibilities:
- Your model is over or under constrained
- Your model constraints are impossible to meet
- Your model constraints have an error
Start by checking the current constraints for errors and ambiguities
Eg: in our case we have 8 items so requiring the Count of the two buckets to be 20 is impossible to meet
My Solver Answer has Strange Numbers?
In solver up to and including Excel 2007, solver would commonly return numbers like 3.5E-18.
This is 0.0000000000000000035, which is effectively 0
If your model returns these, feel free to go through the model and change them to 0, in our model we should also check as the corresponding 1, may in fact be 0.9999999999999999965.
It should be noted that this problem in Solver in Excel 2010 does not occur as often but will still occur.
What and How have you used solver in the past?
What and How have you used solver in the past?
Let us know in the comments below:
28 Responses to “CP024: Customize Excel to boost your productivity”
I think that the most useful customisation that I utilise frequently is some code I found that allows multiple items to be selected from a data validation list. For example one workbook we use lists the business drivers for a project. Another uses this technique to select the staff involved in a particular project. See http://blog.contextures.com/archives/2009/09/18/select-multiple-items-from-excel-data-validation-list/
Another terrific podcast Chandoo! Glad to hear that you, your family, friends and community are recovering well from HurHur.
You did a great job of covering so many of the customization techniques that I use but one that I really like is the addition of those top portion of the quick access tool bar with items that I use often but are not standard to any of the tool bar options.
Thank again Chandoo for the terrific website! It definitely is helping to make me awesome in Excel.
I customise excel toolbars by inserting an icon and dragging it to the appropriate area.
I prefer not to customize (too much).. I use Excel on a work pc, on two pc's at home, and sometimes on other PC's (even on different languages). I've found that if I keep the most "standard" look, I manage to get around on any pc, whatever the language pack.
The only thing I do is "pinning" the most used files on the Windows taskbar. And even then I sometimes forget what I placed where, and look it up manually anyway...
Hi, Chandoo. Thanks for the complete review of customizations. I use most of the items you mention, such as Options to set the default font to “old” Arial rather than Cambria. I’ve also adapted the QAT, adding a button to Repeat last action as well as ones to close the current workbook and the Excel application. Lastly, I developed a personal Add-in that contains macros and changes the ribbon (via Microsoft’s Custom UI editor) to rearrange buttons for functions I always use and adds a new ribbon tab with buttons for my personal macros. For example, one of my most frequently used macros deletes all rows below and columns to the right of a selected cell and resets the Excel used range value for the worksheet (helpful for when I press Ctrl-End).
Thank you again for another great podcast! I always learn something from your podcast/Blog/site. I can't believe I never bothered to look at setting the number of sheets excel creates when you open a New workbook. That will save me time everyday!
I usually create a Personal Macro set to use, as well as creating some custom ribbon and toolbar sets to make my most needed functions handy (I even include some personal macros in these toolbars.) I also spend some time creating some themes to match the Company reporting colors so that my work can easily be incorporated into company communications.
Thanks for helping me be awesome at Excel everyday!
Hi Chandoo - excellent podcast. At the moment I only use the quick access tool bar to add not standard icons. But now I have several techniques that I am going to try. Thanks
excellent podcast!! not enough users maximise their productivity by making Excel more comfortable to work with!!
I use many of the techniques already mentioned (personal macro book, customised QAT/ribbon, etc) but but, instead of adding lot's of buttons I find it's better learn and use the relevant keyboard shortcuts instead of adding buttons for all those functions you use all the time (avoid button overload!!).
Far better to add buttons for functions you don't use often and that are difficult to find/use in their regular guise
I also use a default 'dashboard' workbook that has hyperlinks to a handful of files I use regularly.
also maybe worth mentioning creating default workbook/worksheet 'styles' - to do this create a workbook with the formats you want (fonts, page setup, # of sheets, etc) and save it to your excel start folder with the name BOOK (use SHEET for the sheet template). From then on all new books/sheets will have the same basic formatting
Thanks for the podcast Chandoo, glad you are recovering from the typhoon experience.
Here at work we created 2 template files, a "simple" one and a "large" one. We often have to put together engineering calculations and having these templates makes it so much faster. The simple one has a cover page (used for tracking revisions) and then a sheet set out in our standard format. The large one has the same cover page, then a contents page that has macro buttons to jump to any of the 10 tabs set up in it. And yes, we often use 5-10 tabs when doing our calculations! This makes the navigation much easier and means we can get on with calcs and not have to spend time formatting.
Thanks and enjoy, Oxi
Hi Chandoo – I liked this episode. So far I only use quick access bar to add icons for Macros, special paste etc.. Looking forward to explore some of the techniques shared by you. Thanks
Thanks for the podcast. There's a couple of things I'll have to try.
I've set up a default workbook that's saved to my excel start directory that contains:
* corporate colours and fonts
* a cover sheet
* modified and expanded cell styles
* default table and pivot table styles
* custom page setup settings
Another thing I've tried is creating chart templates which saves a bit of time.
My Quick Access toolbar is jampacked with macros:
- Save all open spreadsheets
- Backup the active workbook to another folder. Useful if I'm making big changes to the spreadsheet that i might want to revert later.
- Copy & Paste special values. Why click two buttons when you can click one?
- Set my preferred number formatting
- Format graphs in company colours
- Apply red/green conditional formatting for growths data. 0% growth is white, 20% growth is green, -20% growth is red
- Format and apply settings to pivot tables as I like them. E.g. Tabular format, no retained items, no style, etc
- Sort items in a pivot filter. Standard Excel capability only lets you sort items if they are in rows or columns not in a filter
- Delete all custom styles. It amazing how many junk styles spreadsheets can accrue, especially when copying in data from other spreadsheets
- Resize and reposition all comments. I swear comments have a mind of their own, constantly moving to bizarre places.
- Print in a Userform all external links and whether the links are active. Including those in name manager and in pivot tables that don't show up in the 'Edit links' window.
- Print in a Userform all HIDDEN name manger names. As a company we need to be careful about what is exposed when we publish spreadsheets.
These (and more I've not mentioned) save me countless hours during a normal working week!
Thanks for a great podcast. Really useful tips on customisation. The tip on only one sheet instead of three - using that now myself.
Personally I use customisation for two main purposes. Quick access to functions I use regularly – to state the obvious – but also some functions I use so infrequently I may not be able to quickly find them when I need them. Forms, for example.
And if I ever need to use a function or command that I have recently learned or used in a new or different way, I add that to the Quick Access Ribbon.
Hi Chandoo,
On top all those customization you've mentioned, I also use the Custom UI Editor for Microsoft Office to create my own Ribbon menu buttons in Excel 2007 and hide the default ones. With the help of macros of course, this makes Excel looks and behave like an App.
Try that to impress your boss !
Chandoo,
Until recently, I had only created custom VBA to solve specific problems related to work. I usually placed a shortcut in a new ribbon. Now I am going to use some of the tips that you mentioned to customize one ribbon for all of the common items that I use (like filter, sort, number format, etc.)
Thank you.
Hi Chandoo,
I really like your podcast. I will appreciate if you continue to do podcast in the future.
Regarding my customize of excel, I usually keep lot of commands in Quick Access Toolbars (QAT), esp, insert/delete sheet row, insert/delete sheet column,copy, cut, format copying, paste, paste special, paste value, Font color, Fill color, camera tool and open recent file etc. Also I click on click on Developer tab so that it is visible on my tabs.
When I was studying MBA, I used to do add-ins of Analysis Toolpak but I have not used that Toolpak since I completed MBA.
Thanking you,
Sam
Hi Chandoo,
I really like your page and it's the first time I listen your podcast and it's great!!. I use a lot the Quick Access Toolbar and also use personal macros for rutine task and for look-and-feel in corporate colors, but after listen you I will try to costumize the ribbon and also I will work with themes and styles.
Thanks to inspire us!!.
Regards from Mexico.
Uriel
Thank you Chandoo, very useful.
I have done 3 things to customize my excel,
Created a new tab and put in it all my frequently used commands.
Recorded all my repeated activities as macros and I am running this everyday.
Added the commands I use very very frequently (including the recorded macros) to the QAT.
Thank you again
Hi Chandoo,
Great podcast. I usually do the following to customize my Excel:
1) I use custom themes and chart & slicer templates
2) Custom macros in QAT and Ribbon for repetitive tasks
3) Keep generic VBA routines in a module for use when needed for specific workbooks, I can just copy it into the target workbook.
Thanks,
Dave
Hi Chandoo,
I have been using the quick access toolbar and it is great for having frequently used features all in one place. As well as macros and those less commonly known features, such as select visable cells when working with hidden rows/columns. The list of all commands available to add to the toolbar is mind numbing.
I did not know about adding your own tab to the ribbon. I have already begun contructing my own.
Thank you for the wonderful information.
Chandoo,
I mainly use the personal macros. There are a few charts that I update frequently, this requires that I keep the old data and change the range of the chart. Changing the range causes Excel to pick all new colors for my chart. So, one macro reverses this issue.
Thanks for sharing your awesomeness.
My customization:
I have three add-ins: Macabacus light for shortcuts (free), XL Campus to work with lots of tabs and the Tableau reshaper add-in (free), to reshape tables in database form.
I have created and copied macros for:
Clean formats
Search and select constants
Format as constant (I used to do financial modeling)
Trace dependents simultaneously
Center across selection (not used anymore since it's in one of the Add-ins)
Search and select blanks cells
Select cell A1 in every sheet (before closing the file)
Protect and unprotect sheets and workbook
Almost all macros have shortcuts and a dedicated tab in the ribbon.
As for Excel options themselves:
Automatic calculations
Error tracking disabled
Cursor stays in same cell when Enter is pressed
And I used to have a Financial modeling template as a predefined sheet where different formats and styles were pre-established
Dear chandoo
Thanks for the excellent podcast. I regularly visit your website and have listened to all your podcast which are very informative. I customise my toolbar by using a quick access and inserting icons in toolbar.
i used all of you suggestions, but have refrained from pinning files to the Recent Workbook List. It bothered me that this pinned files also took over the keybord shortcuts for the last opened files. If I press ALT-F+1, i want to open the last used file, not the file i pinned first.
I missed a very powerful Excel customization option in your podcast, which i use every day and saves me hours: custom keyboard shortcuts. There are two of them:
1. Assign a Key combination to a macro (e.g. "Ctrl-Shift-V" for my VBA-procedure "PasteSpecial_Values")
-> Open the Macro-dialog (Alt-F8) and go to Options, set the key...
2. Assign a Key combination even to F-Keys (e.g. "F5" for "my_favorite_Macro")
-> Open VBA-Editor (Alt-F11), go to any Module in your Personal.xlsb and add this code:
Sub auto_open()
Application.OnKey "{F5}", "my_favorite_Macro"
End Sub
There is no quicker way to call your macro!
Hi Chandoo, very excellent podcast.
I use the quick access toolbar to link my VBA macro's and at the moment I'm experimenting on adding a personal ribbon tab with personal ribbon buttons. I use a Custom UI Editor to do this, it let me link macro's to the buttons used in the personal ribbontab.
This way for a project dashboard I can add the buttons necessary there and they are attached to the file. So other people opening the file have the same ribbon tab. Looking professional and to quote 'awesome' ;-).
Thanks for your prodcast.
I customize my excel in the ribbon. This allows to feature the items I need
Hi Chandoo,
Would you please link me to your Excel Customization Handbook? I am sure that this will help me in a huge way!
Hi Chandoo!
I would love an Excel Customization Handbook! Here is my tip:
To recreate the CTRL-HOME functionality on Excel for Mac copy and paste the following code into your personal macro workbook. I assigned my code to the hotkey Option-Cmd-G and now it's like I have a "Home" button on my Mac!
----------
Sub GoHome()
'
' GoHome Macro
' Simulates Ctrl-Home on a PC
'
' Keyboard Shortcut: Option+Cmd+g
If ActiveSheet.Type = xlWorksheet Then
With ActiveWindow
.ScrollRow = 1
.ScrollColumn = 1
.ActivePane.VisibleRange.Cells(1).Select
End With
End If
End Sub