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cell array indexing oddity

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Robert Scott
Robert Scott on 29 Jul 2021
Answered: Image Analyst on 29 Jul 2021
i have a large cell array of type cell
when i do this
test{2:2:end,7} i get back cells
when i do this i get back ints that are in the cell
test{1,1}
Its very frustrating, I wanted to access all the rows from 2 to the end skipping one in the midding of col 7
Why is that so hard?
It works for a single instance but cant do it in a vectorized form
  6 Comments
DGM
DGM on 29 Jul 2021
A = num2cell(reshape(1:70,10,[]))
A = 10×7 cell array
{[ 1]} {[11]} {[21]} {[31]} {[41]} {[51]} {[61]} {[ 2]} {[12]} {[22]} {[32]} {[42]} {[52]} {[62]} {[ 3]} {[13]} {[23]} {[33]} {[43]} {[53]} {[63]} {[ 4]} {[14]} {[24]} {[34]} {[44]} {[54]} {[64]} {[ 5]} {[15]} {[25]} {[35]} {[45]} {[55]} {[65]} {[ 6]} {[16]} {[26]} {[36]} {[46]} {[56]} {[66]} {[ 7]} {[17]} {[27]} {[37]} {[47]} {[57]} {[67]} {[ 8]} {[18]} {[28]} {[38]} {[48]} {[58]} {[68]} {[ 9]} {[19]} {[29]} {[39]} {[49]} {[59]} {[69]} {[10]} {[20]} {[30]} {[40]} {[50]} {[60]} {[70]}
A{2:2:end,7} % output is multiple scalars
ans = 62
ans = 64
ans = 66
ans = 68
ans = 70
vertcat(A{2:2:end,7}) % output is a single column vector
ans = 5×1
62 64 66 68 70
You need to deal with the fact that that expression has multiple outputs.

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Answers (1)

Image Analyst
Image Analyst on 29 Jul 2021
I know you said you tried using cell2mat(), but you must have not used it correctly. Try using cell2mat() like this:
test = num2cell(reshape(1:80,10,[])) % 10 rows by 8 columns
% Take contents of 7th column and even numbered rows.
% 7th column has 10 elements.
out = cell2mat(test(:,7)); % Get 7th column.
out = out(2:2:end) % Every other element to give 5 elements.
whos test
whos out

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