# How to find column where 0 turns to 1 for each row

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Tanika Bawa am 14 Jul. 2022
Bearbeitet: Bruno Luong am 15 Jul. 2022
Hello!
I would like to be able to find the column (or column title) for each row where the 0 turns to 1.
I have attached example rows (egcolumnsep.mat), so for example for row 5, I would like it to return column 20 (or Bins_11). I would like an output for all the rows though. Some rows might have only 0's (this can be NaN). This basically gives me the reaction time for each row.
Thank you for your help! =)
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Bruno Luong am 15 Jul. 2022
Bearbeitet: Bruno Luong am 15 Jul. 2022
c1 = find(strcmp(DATAb1.Properties.VariableNames,'Bins_1')); % == 10
% Extract relevant data
A = table2array(DATAb1(:,c1:end));
if ~all(ismember(A,[0 1]),'all')
error('Data must be 0 or 1')
end
[cols,rows] = find(diff(A.')==1);
cols = cols+c1;
Idx01 = table(rows,cols)
Idx01 = 37×2 table
rows cols ____ ____ 1 468 1 499 1 855 1 890 2 196 3 452 3 487 3 531 3 828 3 860 4 306 4 338 4 370 4 404 4 434 4 468
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Bruno Luong am 15 Jul. 2022
Bearbeitet: Bruno Luong am 15 Jul. 2022
Why didn't tell us that you are interested only the first transition in the question?
You can call this statement after the above scriot
groupsummary(Idx01, 'rows','min')
or start from scratch
c1 = find(strcmp(DATAb1.Properties.VariableNames,'Bins_1')); % == 10
% Extract relevant data
A = table2array(DATAb1(:,c1:end));
if ~all(ismember(A,[0 1]),'all')
error('Data must be 0 or 1')
end
[a,cols] = max(A,[],2);
cols = (cols+c1-1) .* (a==1) % returns 0 if no transition 0->1 is found
cols = 5×1
468 196 452 306 20

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Jonas am 14 Jul. 2022
Bearbeitet: Jonas am 14 Jul. 2022
yourMat=[0 0 0 0 0;
0 1 1 0 0;
0 0 0 1 0];
where=arrayfun(@(idx)find(diff(yourMat(idx,:))==1,1,'first')+1,1:size(yourMat,1),'UniformOutput',false)'
where = 3×1 cell array
{1×0 double} {[ 2]} {[ 4]}
an empty cell shows that there was not such a change
you could set it to NaN and convert to an normal array by
where{cellfun('isempty',where)}=NaN
where = 3×1 cell array
{[NaN]} {[ 2]} {[ 4]}
where=cell2mat(where)
where = 3×1
NaN 2 4
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Tanika Bawa am 14 Jul. 2022
I did try that and it doesn't really let me do it unfortunately. It gives me this error:
"Unable to concatenate the specified table variables.
Caused by:
Error using categorical/cat (line 56)
Unable to concatenate a double array and a categorical array."
I do need to keep all the columns (because in the end I just want to add a column at the end with the results from this)

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