How can one do this calculation?

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alpedhuez
alpedhuez 2022-7-16
编辑： dpb 2022-7-17
I have a data
Month City Temperature
1 1 25 24 22 19 ...
1 2 21 19 17 16 ...
2 1 23 19 18 17 ..
2 2 20 18 15 13 ..
Then what I like to do is to calculate, for each month, the nth highest temperature from temperature of every city of the month, and then add this info column for each row of this month.
In the above table, for n=2, the second highest temperature in Month 1 is 24, and 20 in Month 2. Thus the output one wants is
Month City 2nd_Hightst_Temp Temperatures
1 1 24 25 24 22 19 ...
1 2 24 21 19 17 16 ...
2 1 20 23 1918 17 ..
2 2 20 20 18 15 13 ..
Thank you in advance.
  2 个评论
Harshit Gupta
Harshit Gupta 2022-7-16
Could you provide a link/attachment of this data?
Image Analyst
Image Analyst 2022-7-16
We'll get to work on it as soon as you attach your data and code to read it in with the paperclip icon. But first read this:
TUTORIAL: How to ask a question (on Answers) and get a fast answer

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采纳的回答

dpb
dpb 2022-7-16
编辑：dpb 2022-7-17
Assuming you put it into a table as @Steven Lord suggested, then
tHi2=maxk(tData.Temperatures,2,2); tHi2=tHi2(:,2); % get top two, keep second only
tData=addvars(tData,tHi2,'before','Temperatures','NewVariableNames',{'2nd Highest Temperature'});
ADDENDUM/CORRECTION:
The second optional argument to operate over the second dimension (by rows) was inadvertently omitted...
  2 个评论
alpedhuez
alpedhuez 2022-7-16
I was able to solve this issue on my end:
  1. for each month, extract temperatures
  2. reshape temperatures in a row vector
  3. run sort to reorder
  4. extract second highest
  5. add second highest value to the matrix
dpb
dpb 2022-7-17
编辑：dpb 2022-7-17
See above comment/correction...moral -- read the doc if it isn't quite right!!! I just whiffed on forgetting to write it down when writing online...

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