square root of sum of squares on portions of cell arrays - Matlab Noob
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I have a cell array, out5, with a single column of 2x1 vectors. I would like to take the square root of the sum of the squares of the two values in each vector for each of these vectors. I was looking at doing some code similar to this:
cellfun(@hypot,out5)
where,
out5 =
[0;0]
[0;-162]
[-54;72]
...
I would desire the output to be:
out6 = [sqrt(0^2 + 0^2) ; sqrt(0^2 + (-162)^2) ; sqrt((-54)^2 + 72^2) ; ... ]
I would also like the values to be either positive or negative depending on the first values in the vectors of out5. so for instance, the third vector in the cell array out5 [-54;72] the value output would be a negative since the first value is negative. In this example the final result would be:
[0 ; 162 ; -90]
3 个评论
Siddharth Pande
2013-3-28
what is your cell an image for example if you are using a image in grey scale the piccture image quality is defined on 100 for white and 0 for black what i mean to say the darkest of the darkest image will also be a positve one so you define your image in positive range
采纳的回答
Sven
2013-3-28
编辑:Sven
2013-3-28
out5 = {[0;0],[0;-162],[-54;72]}
cellfun(@(vec)hypot(vec)*((-2*double(vec(1)<0))+1),out5)
or
cellfun(@(vec)sqrt(sum(vec.^2))*((-2*double(vec(1)<0))+1),out5)
ans =
0 162 -90
The bit at the end: ((-2*double(vec(1)<0))+1)
Will return 1 for a positive (or zero), and -1 for a negative. The sign() function almost does that, but it returns zero for zero, which isn't quite what you want.
4 个评论
Sven
2013-3-28
Mark, the best way to think of cellfun/arrayfun is this:
- Pretend you've got a variable (or variables) with names in the @(name1,name2) part.
- Write a 1-line command that you would do with that/those variables
So in my example I've got cellfun(@( vec )... This means I just have to write something that refers to some variable called vec, and it will actually be the contents of the cell I'm giving. It's basically equivalent to:
for i=1:numel(out5)
vec = out5{i};
% Now I need to do something with *vec*
end
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