How to do pivot from table-type variable

Question

Pete sherer 2018-10-4

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/422239-how-to-do-pivot-from-table-type-variable

回答： Lola Davidson 2023-3-17

采纳的回答： Steven Lord

在 MATLAB Online 中打开

Hi,

I have this table-type data

tdata.yearID=[1950;1950;1950;1951;1951;1951;1951;1952;1952;1952];
tdata.cluster=[1;3;4;1;2;3;4;1;2;3];
tdata.GroupCount=[5;2;6;2;2;4;2;1;2;2];
tdata= struct2table( tdata)

tdata =

10×3 table
    yearID    cluster    GroupCount
    ______    _______    __________
      1           5     
      3           2     
      4           6     
      1           2     
      2           2     
      3           4     
      4           2     
      1           1     
      2           2     
      3           2

Currently I am using this code below to do pivot, but it was very slow for large data. Is there a way to vectorize this code?

[uniqYr, ~, JYr]= unique( tdata.yearID);
nEventData.yearID= [1: 2000]';
[ nEventData.cnt]= zeros( length(nEventData.yearID), 4);
for runYr= 1: length( uniqYr)
    indxYr= uniqYr( runYr);
    tloc  = (JYr== runYr);
    tt    = tdata( tloc, :);
    nEventData.cnt( indxYr, tt.cluster')= tt.GroupCount';        
end % for runYr

So results look like this for rows 1949-1955. Other rows have zeros.

nEventData.cnt (1949:1955,:)

ans =

   0     0     0
   0     2     6
   2     4     2
   2     2     0
   0     0     0
   0     0     0
   0     0     0

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Peter Perkins 2018-10-5

Pete, your code does not run and it's not at all clear what you want as your result. You are going to need to be much more clear.

Peter Perkins 2018-10-5

The updated question and output clarify that unstack does what you need, as Steve suggests.

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Answer 1

Steven Lord 2018-10-5

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/422239-how-to-do-pivot-from-table-type-variable#answer_339957

在 MATLAB Online 中打开

The output you described looks somewhat like the first example in the documentation for the unstack function. I think what you want is something close to the pivotedTdata variable created by this example:

tdata.yearID=[1950;1950;1950;1951;1951;1951;1951;1952;1952;1952];
tdata.cluster=[1;3;4;1;2;3;4;1;2;3];
tdata.GroupCount=[5;2;6;2;2;4;2;1;2;2];
tdata= struct2table( tdata)
pivotedTdata = unstack(tdata, 'GroupCount', 'cluster')

You can retrieve data for a particular year this way:

pivotedTdata(pivotedTdata.yearID == 1950, :)