Grouping calculated values of for loops together

Question

Timo Baumann 2020-2-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/505516-grouping-calculated-values-of-for-loops-together

编辑： Timo Baumann 2020-2-14

采纳的回答： Guillaume

Hi Guys :)

I'd like to group calculated values of for loops together so I can create a boxplot of them.

Suggestions and help would be much appreciated, since I can't find a proper and easy way to do this.

Thank you in advance :)

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Jon 2020-2-14

编辑：Jon 2020-2-14

It is not clear from your question what you are trying to do. Please include the code you have tried so far, and explain what input you have and what output you are hoping to obtain. Show if possible a simple example.

Timo Baumann 2020-2-14

编辑：Guillaume 2020-2-14

在 MATLAB Online 中打开

The following is just a simplified and very short example of what I'd like to do:

e = [0.1 0.2 0.8 0.9]
r = [0.9 1.2 2.8 7.9]
for i = length(e)
    cs=e*2.93*r;
    for d = 70:-1:0
        b=cs^2.*e+d;
    end
end

I'd like to create a boxplot of "cs" and "b" and also be able to store every value of "b" and "cs" in a seperate vector, so I can use them in different plots with other values, that are calculated in a similar fashion in the bigger version of the code.

I was thinking maybe something like this could work:

e = [0.1 0.2 0.8 0.9]
r = [0.9 1.2 2.8 7.9]
for i = length(e)
    cs(i)=e*2.93*r;
    for d = 70:-1:0
        b(i)=cs(i).^2.*e(i)+d;
    end
end

Unfortunatelly it didn't really do what I wanted it to (as stated above).

A table showing every different value of "e", "d" and "r" with the corresponding caclulated value of "cs" and "b" would also be part of what I hope to achieve.

T = table(e,r,cs,d,b);
disp(T)

Using "T = table(...)" didn't quite give me the desired table with all the variables and their respective calculated values in rows and columns and I'm not sure how that could work with nested for-loops (which I don't know how to avoid, since I want to test every value of every variable with one another).

I'm asking a lot at once here sry ^^

But thanks for helping me with at least some suggestions :)

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Answer 1

Guillaume 2020-2-14

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/505516-grouping-calculated-values-of-for-loops-together#answer_415603

在 MATLAB Online 中打开

I'm not entirely clear on what you mean by boxplot nor what you're trying to achieve since none of the pieces of code you posted work. perhaps in the first one you meant to write

e = [0.1 0.2 0.8 0.9]
r = [0.9 1.2 2.8 7.9]
for i = length(e)
    cs=e*2.93.*r;     % .* instead of *
    for d = 70:-1:0
        b=cs.^2.*e+d; % .^ instead ^
    end
end

which at least doesn't error even if it overwrites cs and b on each steps of the loop.

If you meant to create cs for each possible combination of e and r, and create b for each combinatio of e, r and d, then you don't need a loop:

%to create all combinations, the input vectors must each be in a different direction
e = [0.1; 0.2; 0.8; 0.9];  %column vector                   Mx1
r = [0.9, 1.2, 2.8, 7.9];  %row vector                      1xN
d = permute(70:-1:0, [1, 3, 2]); %vector in 3rd dimension,  1x1xP
cs = 2.93 * e .* r;  %2D matrix, MxN
b = cs.^2 .* e + d;  %3D matrix, MxNxP

and to create the desired table:

[ee, rr, dd] = ndgrid(e, r, d);
table(ee(:), rr(:), cs(:), dd(:), b(:), 'VariableNames', {'e', 'r', 'cs', 'd', 'b'})

Note that If you were to use loops the code would go like this:

e = [0.1, 0.2, 0.8, 0.9];  % 1xM
r = [0.9, 1.2, 2.8, 7.9];  % 1xN
d = 70:-1:0;               % 1xP 
cs = zeros(numel(e), numel(r));  %preallocate MxN matrix
d = zeros(numel(e), numel(r), numel(d));  %preallocate MxNxP matrix
for eidx = 1:numel(e)
    cs(eidx, :) = 2.93 * e(eidx) .* r;
    for didx = 1:numel(d)
        b(eidx, :, didx) = cs(eidx, :).^2 .* e(eidx) + d(didx);
    end
end

Overall, much simpler without the loop.

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Timo Baumann 2020-2-14

编辑：Timo Baumann 2020-2-14

Thank you so much :D

That's exactly what I was looking for :)

Maybe one additional question:

When there are more than 2 input vectors (not just "e" and "r", but also "p","z" and"y") how do I have to write them to let them have different directions (as you mentioned in your answer).

When writing:

e = [0.1, 0.2, 0.8, 0.9];

r = [0.9, 1.2, 2.8, 7.9];

p = [0.7 1.4 2.9 9.9];

z = [0.1, 4.2, 1.8, 0.9];

y = [0.9 1.8 2.4 3.2];

It keeps giving me an error.

Sorry for beeing annoying. You've really helped me a lot already with your answer :)

(In one calculation I use e, r, p, z and y so I don't know how to make sure they are in different directions)

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