Thresholding Matrix Within Cell Array

Question

itend 2017-8-29

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/354487-thresholding-matrix-within-cell-array

评论： Cam Salzberger 2017-8-31

Hello,

I have a cell array called output. Each cell within output contains a 1024 x 1024 matrix. I would like to threshold each matrix so that elements below a given value are set to NaN.

I tried using:

output(output < 100000) = NaN;

However, I feel that this is the wrong approach. Intuitively, I want to use a for loop, however, I don't think that will be the most efficient method possible.

Thoughts? Suggestions?

Thanks :)

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Image Analyst 2017-8-29

Why are you using a cell array instead of a regular 3-D array, and why did you want to set it to NaN? What are you going to do with the output array after that?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Cam Salzberger 2017-8-29

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/354487-thresholding-matrix-within-cell-array#answer_279613

编辑：Cam Salzberger 2017-8-31

在 MATLAB Online 中打开

cellfun is your friend here. You can create a local, nested, or regular function to do the NaN-setting, and then just apply it to each element of the cell array:

function A = filterMatrix(A,thresh)
    A(A < thresh) = NaN;
end

Then call it with:

filteredOutput = cellfun(@(A) filterMatrix(A, 100000), output, 'UniformOutput', false);

-Cam

2 个评论
显示无隐藏无

itend 2017-8-29

在 MATLAB Online 中打开

Thank you for your response.

Unfortunately, it produced an error:

f = @(A) A(A < 100000) = NaN;
                        ↑
Error: The expression to the left of the equals sign is not a valid target for an assignment.

What do you think?

Cam Salzberger 2017-8-31

Ah, sorry about that. I forgot you can't do assignment in anonymous functions. Easy enough to make a separate function for it though. I've edited my answer above to function correctly.

Image Analyst has a point though; could you not just create a 3-D matrix originally? That would allow you to do the whole thing in a single call. Also would take less overhead, though it will need a larger contiguous memory chunk.

-Cam

请先登录，再进行评论。