Few days ago, I saw a beautiful homemade science experiment on Sand Pendulums on Bruce Yeany’s YouTube channel. Go ahead and check it out. It is a cool project to do with your kids.
I will try this experiment with kids during school term holidays around Easter. But first, I wanted to try the simulation in Excel.
Simulating sand pendulum pattern in Excel
Take a look at the final simulation.
Pendulum pattern – Lissajous curve
The patterns generated by sand pendulum are nothing but Lissajous curves. We can generate these curves in Excel by using below equations.
- X = A * SIN(a*t + d)
- Y = B * SIN(b*t)
where
- A & B refer to amplitude (the length pendulum travels before reversing its direction) along X & Y axes
- a & b refer to height of pendulum along X & Y axes (if these are same you get a simple pendulum and thus a straight line pattern)
- d refers to degrees of shift (its a bit complex to explain here, but read about phase shift on Lissajous curve Wikipedia page)
- t refers to radians (degrees).
But this will generate a smooth line, how to show sand?
Simple, after computing each pair of (X, Y) we add a small random noise to them. This creates an impression of sand falling from pendulum on to a surface and bouncing off. Let’s define our new equations as,
- X = A * SIN(a*t + d) + jx * rand()
- Y = B * SIN(b*t) + jy *rand()
Where jx & jy are jitter fractions (very small numbers, lest the dots will be too away from original points)
What if the pendulum never stops?
Since we are simulating the movement of a pendulum in Excel, we can choose to have a never stopping pendulum (ie a simple gravity pendulum). In this case A & B values never change.
In real life, A&B will reduce with each oscillation until the pendulum comes to a stop (because there is air drag, friction and other forces at play too).
Let’s look at the chart & VBA
Enough physics & maths. Let’s take a look at the chart & VBA behind this simulation.
- Set up 3 columns, one with t values starting from 0 and increasing by 0.05 per cell, next two with X & Y values.
- Leave the X&Y values blank. We will use VBA to fill these.
- Let’s say we use 5000 (x,y) values to plot the chart. This gives enough variation. You can alter the number of rows later.
- Create a scatter plot with smoothed line using these 5000 (x,y) values.
- Using VBA, iterate thru column t and calculate X & Y values for each t value using above equations.
- Update the chart by using doEvents after every n calculations. Try n=25 first and change as you see fit. Updating the chart after every calculation slows down the animation significantly.
- Change A, B, a, b, d, jx, jy and air drag factors to generate different curves.
Here is the VBA code used for the animation.
Sub animate()
Dim xVal As Double, yVal As Double, jx As Single, jy As Single
Dim t As Range
Dim a1 As Single, drag As Single
Dim a2 As Double, b2 As Double, d As Double
Dim updateScreen As Integer
Dim tVals As Range
a1 = 1
drag = Range("air.drag")
a2 = [a.2]
b2 = [b.2]
jx = [j.x]
jy = [j.y]
d = WorksheetFunction.pi() / Range("d")
Set tVals = Range("t.vals")
Range(tVals.Offset(, 1), tVals.Offset(, 2)).ClearContents
Range("done") = "drawing..."
For Each t In tVals
xVal = a1 * Sin(t * a2 + d) + jx * Rnd()
yVal = a1 * Sin(t * b2) + jy * Rnd()
t.Offset(, 1).Value = xVal
t.Offset(, 2).Value = yVal
'update screen after every 25 times this loop has run
updateScreen = IIf(updateScreen = 25, 0, updateScreen + 1)
If updateScreen = 0 Then DoEvents
'Reduce A & B values by using drag
a1 = a1 * (1 - drag)
Next t
Range("done") = "done"
End Sub
Download Pendulum Sand Patterns Workbook
Click here to download the Pendulum Sand patterns workbook. Play with the animate & random pattern buttons to see some cool patterns.
Have you done this experiment?
This is a cool way to teach kids the awesome pattern power of simple things in life. Have you done this experiment? If not, give it a try. If you think playing with sand is too messy, try the Excel workbook.
Also check out: 3D dancing pendulums post to see some cool & clever animations. Huge collection of spreadsheet tools & simulations for teachers.
40 Responses to “Looking up when the data won’t co-operate (case study)”
Nice Trick.. Clever use of cell references
Here is a formula I tried to create:
=SUMPRODUCT(((NOT(ISERROR(SEARCH(L5,B4:H14))))*1),(B5:H15))
It takes care of Caveat #1 (can handle text), but Caveat #2 remains.
In situations like this, I will often use VBA to restructure the data (2 columns: dates and values) on to a new worksheet. I can then use this 'clean' source for data analysis (formula or pivot table).
=SUMPRODUCT(((NOT(ISERROR(SEARCH(L5,B4:H14))))*1),(B5:H15)) and complex formulae in general are all very well but when you come back to them in a few weeks / months time, it is not at all easy to see what they do and what the limitations are.
Hi Chandoo,
I had used this type of cell ref. various times while calculating average.
But for the situation here try below formula . Note this is an array formula and must be confirmed with Ctrl+Shift+Enter.
=SMALL(IF(MMULT((L5=B4:H14)*IF(ISNUMBER(B5:H15),B5:H15),{1;1;1;1;1;1;1}),MMULT((L5=B4:H14)*IF(ISNUMBER(B5:H15),B5:H15),{1;1;1;1;1;1;1})),1)
Regards,
Hi, I think Using SEARCH in here will create a problem say there is a text like SUN and another text SUNLIGHT both result will be added by SUMPRODUCT.
Regards,
Array option.
=SUM(IF(MOD(ROW(B4:B14),2)=MOD(ROW(B4),2),IF(B4:H14=L5,B5:H15)))
Regards
@Elias,
Nice approach.
Although not requested - the formula I suggested closes all possibilities.
Criteria: _____ Value to retrieve:
Date__________ Numeric
Date__________Textual
Textual________Numeric
Textual________Textual
While your formula copes with only the 3 first combinations.
Michael (Micky) Avidan
“Microsoft® Answer” – Wiki author & Forums Moderator
“Microsoft®” MVP – Excel (2009-2015)
ISRAEL
@Michael,
Sorry but I don’t understand your point. I believe the challenge was to return the summary of a given date. What is your really volatile formula doing that mine is not?
Regards
@Elias,
I didn't say that the challenge differs from what you just mentioned/aimed to nor that your formula doesn't provide the requested result.
Please read my previous comment again and focus on the last combination (TEXT / TEXT).
I, myself, always try to provide a global Formula that is capable to handle all sorts of data.
Michael (Micky) Avidan
“Microsoft® Answer” – Wiki author & Forums Moderator
“Microsoft®” MVP – Excel (2009-2015)
ISRAEL
@Michael,
I see your point, but you are missing the below points if you are trying to cover all sorts of data.
What happened if the lookup value does not exist?
Do you want the first, second, summary, concatenation of the values if the look value is repeated?
See they are too many possibilities to be cover with just one formula.
Regards
1) The range: B4:H15 was named: RNG.
2) The following Array Formula was "retrieved from my sleeve" and I hope it can be shorten.
3) The formula seems to take care of BOTH(!) caveats.
-------------------------------------------------------------------------------
=OFFSET(INDIRECT(ADDRESS(SMALL(IF(RNG=L5,ROW(RNG),""),1),MOD(SMALL(IF(RNG=L5,(ROW(RNG))+COLUMN(RNG)/10),1),1)*10)),1,)
-------------------------------------------------------------------------------
Michael (Micky) Avidan
“Microsoft® Answer” – Wiki author & Forums Moderator
“Microsoft®” MVP – Excel (2009-2015)
ISRAEL
@Michael,
Check what happened with your result if you type 41927 in D5.
Regards
Correct. Didn't predict that.
Will find time to work something out.
Michael (Micky) Avidan
“Microsoft® Answer” – Wiki author & Forums Moderator
“Microsoft®” MVP – Excel (2009-2015)
ISRAEL
@Elias,
Let's hope the following Array Formula "closes all open doors".
Again - it has nothing to do with your formula which works fine as long as the 3 first mentioned combinations are concerned.
-------------------------------------------------------------------------------
=INDEX(RNG,LARGE(IF(RNG=L5,MOD(ROW(RNG)-1,2)*(ROW(RNG)),""),1)-2,(MOD(SMALL(IF(RNG=L5,(ROW(RNG))+COLUMN(RNG)/10),1),1)*10)-1)
-------------------------------------------------------------------------------
Michael (Micky) Avidan
“Microsoft® Answer” – Wiki author & Forums Moderator
“Microsoft®” MVP – Excel (2009-2015)
ISRAEL
Ok, if you insist. The following will cover all the scenarios you listed. However, I’ll never recommend/use such of formula.
Defined names:
rDat = $B$4:$H$15
rRow =ROW(rDat)-MIN(ROW(rDat))+1
rCol =COLUMN(rDat)-MIN(COLUMN(rDat))+1
rInc =MOD(rRow,2)=MOD(MIN(rRow),2)
L6=INDEX(rDat,MAX(IF(rInc,IF(rDat=L5,rRow)))+1,MAX(IF(rInc,IF(rDat=L5,rCol))))
Array Enter
Regards
@Michael,
unfortunately, your array formula still seems to return wrong results (eg 3-Nov).
If data are organized like in the example, ie. looks like a calendar, the INDEX formula seems quite simple:
=INDEX($B$4:$H$15,ROUNDDOWN((L5-B4)/7,0)*2+2,MOD((L5-B4),7)+1)
Yours is effectively the same as what I just came up with, and I believe this is the optimal answer to this particular problem.
My solution, before I saw yours:
=OFFSET(B5,QUOTIENT(L5-B4,7)*2,MOD(L5-B4,7))
OFFSET will work for an arbitrary list size, but INDEX might be easier to read.
QUOTIENT does the round and division in a single step.
If there's an improvement over Elias's solution then I for one can't see it.
Perhaps a non-CSE version which would also mean that only two references (B4:H14 and B5:H15), as opposed to three (B4, B4:B14 and and B5:H15), would require manually amending should the data range change, i.e.:
=SUMPRODUCT((ISEVEN(ROW(B4:H14)-MIN(ROW(B4:H14)))*(B4:H14=L5)*B5:H15))
I suppose we could make it a single, uniform range reference:
=SUMPRODUCT((ISEVEN(ROW(B4:H14)-MIN(ROW(B4:H14)))*(B4:H14=L5)*OFFSET(B4:H14,1,,,)))
which might be more appropriate should we e.g. wish to use a Defined Name for our range, i.e.:
=SUMPRODUCT((ISEVEN(ROW(Rng)-MIN(ROW(Rng)))*(Rng=L5)*OFFSET(Rng,1,,,)))
though whether that compensates for the extra, volatile function call is something to be debated.
Regards
I have tried something and then my Excel workbooks got shut down. Maybe that was too much?
Anyway here is what I've tried:
=SUMPRODUCT(INDEX(B5:H15;IF(ISEVEN(ROW(B5:H15));ROW(B5:B15)-ROW(B5)+1);{1\2\3\4\5\6\7}))
Guess that was wrong? Would this approach work anyway?
Looking forward to learn something from you Excel Experts.
Sorry, I haven't took notice of XOR LX's answer. I guess that's kind of what I was looking for.
@Michael Avidan
As it stands that is not a very rigorous construction.
You say "I, myself, always try to provide a global Formula that is capable to handle all sorts of data", which is a wonderful philosophy, but isn't it at least as important that we ensure that our formulas are independent of the row and column references of the data range in question, so that, should that range change, we do not have to re-work our solution?
What happens with your formula, for example, if RNG is instead re-located one row down, from B4:H15 to B5:H16?
When a formula is reliant upon the addition/subtraction of certain constants within the formula, which themselves are necessarily dependent upon the specific rows/columns in which the data lies at any given time (e.g. the -1 in MOD(ROW(RNG)-1,2)), then that formula is not a very flexible one.
Hence the reason for my choice of a slightly longer construction:
ROW(B4:H14)-MIN(ROW(B4:H14))
which ensures that this part of the calculation is not dependent upon the precise location of the data range within the worksheet, and so will give correct answers even if that range is re-located.
Regards
{=OFFSET(B4,MAX((B4:H15=L5)*ISODD(ROW(1:12))*ROW(1:12)),MAX((B4:H15=L5)*ISODD(ROW(1:12))*COLUMN(A:G))-1)}
Non-array formula:
=INDEX(B4:H15,SUMPRODUCT((B4:H15=L5)*(ROW(B4:H15)-ROW(B4)+1)*ISODD(ROW(B4:H15)-ROW(B4)+1))+1,SUMPRODUCT((B4:H15=L5)*(COLUMN(B4:H15)-COLUMN(B4)+1)*ISODD(ROW(B4:H15)-ROW(B4)+1)))
Using one range (B4:H15), one reference (B4), one lookup value (L5) and no INDIRECT or OFFSET.
My trial with defined names:
DateRange
=$B$4:$H$4,$B$6:$H$6,$B$8:$H$8,$B$10:$H$10,$B$12:$H$12,$B$14:$H$14
Position
=RANK('lookup problem'!$L$5,DateRange,1)
L6
=OFFSET(B4,ROUNDUP(Position/7,0)*2- 1,IF(MOD(Position,7)=0,6,MOD(Position,7)-1))
I'd probably just run with something like:
=SUMPRODUCT((B4:H14=L5)*(MOD(ROW(B4:H14),2)=MOD(ROW(B4),2))*B5:H15)
...which is basically the same as Elias' but without the IFs
The opposite of elegant but it works...
=INDEX(B4:H15,IFERROR(MATCH(L5,B4:B14,0),0)+IFERROR(MATCH(L5,C4:C14,0),0)+IFERROR(MATCH(L5,D4:D14,0),0)+IFERROR(MATCH(L5,E4:E14,0),0)+IFERROR(MATCH(L5,F4:F14,0),0)+IFERROR(MATCH(L5,G4:G14,0),0)+IFERROR(MATCH(L5,H4:H14,0),0)+1,IFERROR(MATCH(L5,B4:H4,0),0)+IFERROR(MATCH(L5,B6:H6,0),0)+IFERROR(MATCH(L5,B8:H8,0),0)+IFERROR(MATCH(L5,B10:H10,0),0)+IFERROR(MATCH(L5,B12:H12,0),0)+IFERROR(MATCH(L5,B14:H14,0),0))
=INDEX(B4:H15,
IFERROR(MATCH(L5,B4:B14,0),0)+
IFERROR(MATCH(L5,C4:C14,0),0)+
IFERROR(MATCH(L5,D4:D14,0),0)+
IFERROR(MATCH(L5,E4:E14,0),0)+
IFERROR(MATCH(L5,F4:F14,0),0)+
IFERROR(MATCH(L5,G4:G14,0),0)+
IFERROR(MATCH(L5,H4:H14,0),0)+1,
IFERROR(MATCH(L5,B4:H4,0),0)+
IFERROR(MATCH(L5,B6:H6,0),0)+
IFERROR(MATCH(L5,B8:H8,0),0)+
IFERROR(MATCH(L5,B10:H10,0),0)+
IFERROR(MATCH(L5,B12:H12,0),0)+
IFERROR(MATCH(L5,B14:H14,0),0))
Named Range
rownum = SUMPRODUCT(('lookup problem'!$B$4:$H$14='lookup problem'!$L$5)*ROW('lookup problem'!$B$4:$H$14)*ISEVEN(ROW('lookup problem'!$B$4:$H$14)))
Formula
=OFFSET($A$1,rownum,MATCH(L5,INDIRECT("$B"&rownum&":$H"&rownum),0))
How about SUM(IF(B4:H14=L5,B5:H15)) with array..it should work
Sorry, Chandoo, you can't find stuff this way in every possible scenario.
What if 2014-10-01 sales would equal 41.927 ? Which is serial number for 2014-10-15 ? SUMIF would fail to retrive correct answer. And your example data suggest that such number is possible in your table.
It's better not to search through dates and numbers at the same time.
If I'd solve a problem like this, it'd reformat table first so I get one column with dates and the other with numbers.
In this case, formula to form date column would be:
=INDIRECT(ADDRESS((INT((ROW()-4)/COUNT($B$4:$H$4))+1)*2+2;MOD(ROW()-4;COUNT($B$4:$H$4))+2;4;1))
and numbers would be the same formula with sight adjustment (+3 instead of +2 at the end of first argument):
=INDIRECT(ADDRESS((INT((ROW()-4)/COUNT($B$4:$H$4))+1)*2+3;MOD(ROW()-4;COUNT($B$4:$H$4))+2;4;1))
And now you got two columns that you can safely use for searching!
Oops, sorry, you actually mentioned that it doesn't work if number=date! I missed that part 🙁
={OFFSET(A1,SUM((B4:H14=L5)*ROW((B4:H14))),SUM((B4:H14=L5)*COLUMN((B4:H14)))-1)}
Works for all data... the solution I got for indirect looks little lengthy
I want to count last 20 records of a person, whose marks is greater than 2 and grade "manager". ....
Assume A1 has got names (James, John...etc...)
A2 "Manager"
A3 "2"
Someone please reply
I want to count last 20 records of a person, whose marks is greater than "2" and grade "Manager"
Assume A1 "geroge" A2 "Michael" A3 "George" etc...name can found anywhere in the rows
B1 "Manager" B2" clerk"
C1 "2" C2, "4"
please reply
Simplest I can come up with. No limitations for either 1 or 2. This does assume dates are an ordered list with 7 per row, and 2 rows per set. Assuming this is always true this will work for an arbitrary long list of dates.
=OFFSET(B5,QUOTIENT($L$5-$B$4,7)*2,MOD($L$5-$B$4,7))
@Marc,
Nice approach - however, as there are no "Negative Dates" - try:
=OFFSET(B5,INT(L5-B4)/7)*2,MOD(L5-B4,7))
——————————————————————————-
Michael (Micky) Avidan
“Microsoft® Answer” – Wiki author & Forums Moderator
“Microsoft®” MVP – Excel (2009-2015)
ISRAEL
=OFFSET(B4,ROUNDUP((L5-41911+1)/7,0)*2-1,MOD(L5-41911,7))
B4 has been used as reference cell for OFFSET().
FOR ROWS:
ROUNDUP(....,0) gives the integer value of a division. In case of presence of a remainder, ROUNDUP will add 1 to the Quotient.
As opposed to ROUNDUP(), the INT() or QUOTIENT() functions eliminate the remainder.
41911 = 01-Sept-2014, the first date in the data.
*2 has been used because there are 2 columns per set of data.
/7 has been used because there are 7 columns per set of data.
For columns
MOD(L5-41911,7))
Vijaykumar Shetye,
Panaji, Goa, India
This is how i did it
{=INDEX(B4:H15, MAX((L5=B4:H15)*ROW(B4:H15))-2, MAX((L5=B4:H15)*COLUMN(B4:H15))-1 )}
Here's my solution:
=INDEX(B4:H15,MATCH(1,MMULT(--(B4:H15=L5),TRANSPOSE(COLUMN(B4:H15)^0)),0)+1,MATCH(1,MMULT(TRANSPOSE(--(B4:H15=L5)),ROW(B4:H15)^0),0))
Sorry, forgot to mention Ctrl Shift Enter is needed.