Excel Speedup & Optimization Tips by Experts [Speedy Spreadsheet Week]

Excel Speeding up & Optimization Tips by Hui

About Hui:
Hui (Ian Huitson) has been writing & contributing to Chandoo.org for more than 2 years. Many of you know him from Formula Forensics & Data table related articles on Chandoo.org. See about Hui page for more about him.

In no particular order:

• Minimize the use of Volatile Functions
• Organize your workbook layout and data methodically
• Where possible use fixed values or Named formulas instead of lookups even if the values only change rarely, flag those for manual checking
• Don’t Start equations with a + that actually adds 0.4% calculation time
• Minimize use of the Data Table command to running summaries only at the end of a project
• Review the logic of the model and all if’s or lookup choices for necessity or alternatives
• Use negatives instead of multiple positives where appropriate in conjunction with If’s and Lookups
• Learn about Conjunctive Truth Tables, they Rock for reporting
• Array formulas can do the work of dozens of normal cells, but use cautiously
• Use Named Formulas and UDF’s instead of multiple Helper Cells/Rows or Columns
• Minimize of us Conditional Formatting
• Minimize use of linked workbooks especially if over network drives
• Take an advanced Excel course like the ExcelHero Academy
• Minimize the use of Excel 2007

Links:

• http://www.decisionmodels.com/calcsecretsi.htm
• http://msdn.microsoft.com/en-us/library/bb687891.aspx
• http://www.ozgrid.com/News/GoodVsBadDesignSpeedUpEvents.htm

Excel Speeding up & Optimization Tips by George

About George:
George runs Excel Unusual, where you can learn about using Excel for engineering, simulations & games. In his work, he builds complex spreadsheet models all the time. So I asked him to share a few tactics with us. He wrote 2 articles in response to my request.

Links:

• http://excelunusual.com/archive/2012/03/about-the-speed-of-spreadsheets-1/
• http://excelunusual.com/archive/2012/03/about-the-speed-of-spreadsheets-2/

Excel Speeding up & Optimization Tips by Gregory

About George:
Gregory runs Excel Semipro, where he shares Excel tips & ideas. I asked him to contribute to the Speedy Spreadsheet Week. This is what he says,

Tips by George:

To speed up my worksheet files, I have one primary rule: do not use the OFFSET function, which is volatile and can slow things down considerably. In newer spreadsheets I use Tables and The imposing INDEX function to keep ranges automatically updated. In Excel 2003 I use an event-based approach, with named ranges, the worksheet deactivate module, and VBA to keep lists and ranges updated.

Links:

• The Imposing INDEX
• How to Update a List or Range without OFFSET
• Example worksheet
  

Excel Speeding up & Optimization Tips by Luke

About Luke:
Luke is one of the Excel Ninjas at Chandoo.org where he contributed more than 1000 posts. I asked Luke to share some optimization tips based on his vast experience of using Excel & helping others. This is what he suggests:

1. In VB, whenever I see a line like Selection.something that’s usually an indicator that I’m using extra lines. Either I need to apply the method directly to the object instead of selecting it, or I need to use a With statement.
2. With Event macros, don’t forget the all-important lines of Application.EnableEvents = False and Application.EnableEvents = True so that you don’t cause multiple events to be triggered.
3. See a section of code that you’re repeating? Probably need to make this a separate Sub or Function that you can then reference from the main code.
4. When building your formula page, think top-down. Cells near the top of worksheet should be referenced in formulas that are below, not vice-versa. XL likes to calculate left to right, top to bottom. Scattering cell references around makes it work harder.
5. When using large amounts of data that you want to be charted, sometimes I’ll build a formula sheet within the workbook with data, and then just build another workbook that uses a data query (referencing the formula results) to generate the charts.
6. This might be more along the lines of auditing a worksheet, but sometimes it’s hard to see how I’ve laid out my constants and formulas, and using a worksheet map helps bring things into focus (related: create a worksheet map)

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Excel Speeding up & Optimization Tips by Narayan

About Narayan:
Narayan is one of the Excel Ninjas at Chandoo.org where he contributed more than 1000 posts. I asked Narayan to share some optimization tips based on his vast experience of using Excel & helping others. This is what he suggests:

Period-to-Date and Cumulative SUMs
There are two methods of doing period-to-date or cumulative SUMs. Suppose the numbers that you want to cumulatively SUM are in column A, and you want column B to contain the cumulative sum; you can do either of the following:
You can create a formula in column B such as =SUM($A$1:$A2) and drag it down as far as you need. The beginning cell of the SUM is anchored in A1, but because the finishing cell has a relative row reference, it automatically increases for each row.
You can create a formula such as =$A1 in cell B1 and =$B1+$A2 in B2 and drag it down as far as you need. This calculates the cumulative cell by adding this row’s number to the previous cumulative SUM.
For 1,000 rows, the first method makes Excel do about 500,000 calculations, but the second method makes Excel do only about 2,000 calculations.

Subtotals
Use the SUBTOTAL function to SUM filtered lists. The SUBTOTAL function is useful because, unlike SUM, it ignores the following:
Hidden rows that result from filtering a list. Starting in Excel 2003, you can also make SUBTOTAL ignore all hidden rows, not just filtered rows.
Other SUBTOTAL functions.

Using SUMPRODUCT to Multiply and Add Ranges and Arrays.
In cases like weighted average calculations, where you need to multiply a range of numbers by another range of numbers and sum the results, using the comma syntax for SUMPRODUCT can be 20 to 25 percent faster than an array-entered SUM.
{=SUM($D$2:$D$10301*$E$2:$E$10301)}
=SUMPRODUCT($D$2:$D$10301*$E$2:$E$10301)
=SUMPRODUCT($D$2:$D$10301,$E$2:$E$10301)
These three formulas all produce the same result, but the third formula, which uses the comma syntax for SUMPRODUCT, takes only about 77 percent of the time to calculate that the other two formulas need.

Dynamic Ranges

These are most often created using the OFFSET and COUNTA functions , as in the following :
=OFFSET(Sheet1!$A$1,0,0,COUNTA(Sheet1!$A:$A)-1,1)

Sometimes , when data is stored in the form of records , so that all columns have data to the same extent , there may be several dynamic ranges ; say we have ORDER_ID in column A , CUSTOMER_ID in column B , and the AMOUNT in column C. Thus there may be several dynamic ranges as follows :
=OFFSET(Sheet1!$A$1,0,0,COUNTA(Sheet1!$A:$A)-1,1)
=OFFSET(Sheet1!$B$1,0,0,COUNTA(Sheet1!$B:$B)-1,1)
=OFFSET(Sheet1!$C$1,0,0,COUNTA(Sheet1!$C:$C)-1,1)
These can be simplified to :
=OFFSET(Sheet1!$A$1,0,0,COUNTA(Sheet1!$A:$A)-1,1)
=OFFSET(Sheet1!$B$1,0,0,COUNTA(Sheet1!$A:$A)-1,1)
=OFFSET(Sheet1!$C$1,0,0,COUNTA(Sheet1!$A:$A)-1,1)
These can then be optimized by storing the COUNTA value in a cell , and using the cell reference within the OFFSET formula :
=OFFSET(Sheet1!$A$1,0,0,Sheet1!$F$1,1)
=OFFSET(Sheet1!$B$1,0,0, Sheet1!$F$1,1)
=OFFSET(Sheet1!$C$1,0,0, Sheet1!$F$1,1)
Where Sheet1!$F$1 contains the formula : =COUNTA(Sheet1!$A:$A)-1
For more, refer to MSDN.

Resetting the USED RANGE

Pressing CTRL END will take the cursor and place it on the cell which Excel thinks is the last used cell in the worksheet.
Suppose you do this , and the cursor lands on D27 ; now navigate to any cell which is as far away as you can imagine , say AA3456 ; enter any character , even a space will do ; then clear the cell contents by pressing the DEL key.
Pressing CTRL END will now take the cursor to AA3456.
To reset the USED RANGE , go to the Immediate Window of the VBA Project , and enter the following statement :
Application.ActiveSheet.UsedRange
Your used range should now be reset to its earlier value of D27 ; pressing CTRL END will now take the cursor to D27.
Refer to this Stackoverflow discussion for more.

Excel Speeding up & Optimization Tips by Jordan

About Jordan:
Jordan runs Option Explicit, an Excel VBA blog. He shared these tips with us,

• When reading and writing to ranges, use .value2 (this is noticeable for large, iterative calculations)
• Ensure that ALL spreadsheet errors are handled. The most common errors I see ignored are #Ref errors and #Div (for dividing by zero). Use Go To Special… to find these errors and either delete them or use IFERROR to handle them. In my opinion, Excel errors are one of the biggest contributing factors to slow spreadsheets.
• When using INDEX, include the row or column number even if you don’t need it. For example, if I’m pulling data from only one column, I need only write =INDEX(A1:A10, 1) to pull the first item. However, =INDEX(A1:A10, 1, 1) appears to be a hair faster. Try it.
• Cut down on Lookup functions. In many instances, the lookup table has already encoded information in the correct order. Instead of looking up, say, Stage 2, just use INDEX on the desired column and pull from row 2.

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