How to output function results over split columns
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I have a loop which contains a function that produces results to a different sheet of a matrix. I would like to insert an additional column of information after the function has been completed, but I am not sure how to index the function output to allow for this. Ideally, I would like to collect the output information into a split set of columns so my inserted column is in the middle, but I either receive a 'Subscripted assignment dimension mismatch' or 'Undefined function or variable 'output'' error (depending on if I initialize with a blank array or not).
for i = 1:N;
output(:,[1:4,6:end],i+1) = processFiles(input);
output(:,5,i+1) = output(:,4,i+1)./output(:,2,i+1);
end
Does anybody have a suggestion on how to go about doing this type of insertion?
(Before you ask, no, I cannot provide a sample of 'input' or the 'processFiles' function)
Thanks
3 个评论
TADA
2019-1-24
Set The Output Of processFiles Into A Matrix Regularly, Then Concat All Three Parts Of The Data Into Your Output Matrix
Bob Thompson
2019-1-24
TADA
2019-1-24
I'm Not Sure If It's Possible Or Not, I Never Tried This Type Of Indexing. But I Beg To Differ About "Simplicity's Sake".
The Complex Indexing Seems Less Clear Than Doing It With The Intermediate
Think About The Next Person Reading Your Code, or Yourself Reading It A Year From Today.
采纳的回答
Figured it out...
the problem is you use the end operator with a matrix that's not asigned yet
or when you do preset it to a different size the end operator returns a value thats not large enough to accomodate your output matrix (or too big for that matrix, still mismatching)
Here is my mock code:
clear;
n = 8;
N = 3;
output = zeros(n, n+1, N+1);
for i = 1:N
output(1:8, [1:4,6:end], i+1) = processFiles(n);
output(:,5,i+1) = output(:,4,i+1)./output(:,2,i+1);
end
output
function out = processFiles(in)
out = repmat(1:in,in,1);
end
Now, when you change the preallocation line:
clear output; % output not predefined, end operator throws Undefined function or variable 'output'
output = zeros(8,9,4); % the sizes generated by the mock code - works fine.
output = zeros(0,9,0); % will reallocate the matrix each iteration
% but works fine because the end operator is used only on the x dimention
output = zeros(0,0,0); % or an empty matrix [] - throws Subscripted assignment dimension mismatch error
% because 6:end returns an empty array
I'm guessing you have a problem with the preallocation, fix that and your indexing will probably work...
As for simplisity, that's completely up to you of course...
4 个评论
Bob Thompson
2019-1-29
TADA
2019-1-29
I currently have 2017b, although i'm pretty sure it should work the same
it is an empty array of size 0x9x0
in the above demo, this array is reallocated each iteration,
initial size: [0 9 0]
size after iteration #1: [8 9 2]
size after iteration #2: [8 9 3]
size after iteration #3: [8 9 4]
so this is generally not a good idea, but it works because the end operator used on the 2nd dimention provides the correct index - 9
Bob Thompson
2019-1-29
TADA
2019-1-29
sorry, I changed your colon into a vector 1:8, thats the difference...
the colon operator alone is all the indices in that dimention, so when the size is 0, it's like writing 1:0
thats the source of that error, I didn't notice that before... again a good preallocation will solve that issue
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