cell array indexing oddity

2021 7 29
1 个回答
更新时间：2021 7 29
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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

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Walter Roberson
Walter Roberson 2021-7-29
Could you confirm that you want 2:2:end, every other row "skipping one each time", and not 2:end (every row skipping one row, namely row 1) ?
imported_data{1,1} is not necessarily the same datatype as the other entries in the cell.
imported_data{2:2:end,7}
Could you confirm that is what you are using? If there are at least 4 rows, that would be "cell expansion", resulting in a "comma separated list" of values, rather than a single value. You would often then need to capture the values somehow, such as {imported_data{2:2:end,7}} or vertcat(imported_data{2:2:end,7}) or horzcat(imported_data{2:2:end,7})
Robert Scott
Robert Scott 2021-7-29
i am using exactly that
imported_data{2:2:end,7}
DGM
DGM 2021-7-29
Ran in:
Ran in:
You're going to have to demonstrate a working example of your problem.
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]}
vertcat(A{2:2:end,7})
ans = 5×1
62 64 66 68 70
Robert Scott
Robert Scott 2021-7-29
i am trying to multiple the values in that cell array by a scalar and have tried just about every trick in the book
dot operator
cell2mat
i literally cant get anything to work
I have opened the data and verified line by line by line by line that they are all the same type yet cell2mat wont work either
nor can i multiple the thing by a scalar
Robert Scott
Robert Scott 2021-7-29
编辑：Robert Scott 2021-7-29
K>> test{2:2:end,7}*1
Error using *
Too many input arguments.
DGM
DGM 2021-7-29
Ran in:
Ran in:
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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回答（1 个）

Image Analyst
Image Analyst 2021-7-29

0 个投票

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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