Why am I not getting desired values using loop?

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Rakesh 2022-7-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1762045-why-am-i-not-getting-desired-values-using-loop

回答： Torsten 2022-7-19

采纳的回答： Jeffrey Clark

在 MATLAB Online 中打开

I have data like

br_peaks =

Columns 1 through 15

0.0002 0.2118 0.4623 0.7067 0.9873 1.2611 1.5412 1.8127 2.0791 2.3712 2.6544 2.9500 3.2134 3.4818 3.7596

Columns 16 through 19

4.0461 4.3143 4.5847 4.8658

I want to make another data in spicific manner. For each value, I will subtract it from three forward points and three backward points and save it in another variable, points(say). I code this using for loops but I am getting only negative points but it should have positive points also.

my code is below. Could anyone help me where did mistake?

br_peaks = [ 0.0002    0.2118    0.4623    0.7067    0.9873    1.2611    1.5412    1.8127    2.0791    2.3712    2.6544    2.9500    3.2134    3.4818    3.7596...
     4.0461    4.3143    4.5847    4.8658]
br_peaks = 1×19
    0.0002    0.2118    0.4623    0.7067    0.9873    1.2611    1.5412    1.8127    2.0791    2.3712    2.6544    2.9500    3.2134    3.4818    3.7596    4.0461    4.3143    4.5847    4.8658
for iii = 1:length(br_peaks)
     for jj = 1:length(br_peaks)
         if iii<3 && br_peaks(jj)<br_peaks(iii+3) 
              points(jj) = br_peaks(jj)-br_peaks(iii);
         elseif iii+3 > length(br_peaks) && br_peaks(jj)>br_peaks(iii-3)||br_peaks(jj)>br_peaks(iii)   
              points(jj) = br_peaks(jj)-br_peaks(iii);
         elseif iii>=3 && br_peaks(jj)>br_peaks(iii-2) && br_peaks(jj)<br_peaks(iii+3)
              points(jj) = br_peaks(jj)-br_peaks(iii);
          
         end
     end
end

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Torsten 2022-7-19

编辑：Torsten 2022-7-19

[1 2 3 4 5 6 7]

Step 1, subtracting 1 from the three forward points:

[1 1 2 3 5 6 7]

Step 2, subtracting 2 from 1 backward and three forward points:

[-1 2 1 2 3 6 7]

Step 3, subtracting 3 from 2 backwards and three forward points:

[-2 -1 3 1 2 3 7]

...

Step 7, subtracting 7 from 3 backward points:

[1 2 3 -3 -2 -1 7]

Now you have 7 result vectors.

Is it that what you want ?

If not, modify the example accordingly.

Rakesh 2022-7-19

Yes, this is what I want to get.

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采纳的回答

Jeffrey Clark 2022-7-19

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1762045-why-am-i-not-getting-desired-values-using-loop#answer_1010930

在 MATLAB Online 中打开

lbr = length(br_peaks);
points = nan(lbr,7); % each row is 1->lbr; cols for a row are nan filled
                     % could change to cells of variable length arrays
for iii = 1:lbr
    k = 1;
    for jj = max([1,iii-3]):min([iii+3,lbr]) % could rewrite loop to one statement instead
        points(iii,k) = br_peaks(jj)-br_peaks(iii);
        k = k+1;
    end
end % after rewrite of inner loop probably could rewrite to one statement

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更多回答（1 个）

Torsten 2022-7-19

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1762045-why-am-i-not-getting-desired-values-using-loop#answer_1011095

在 MATLAB Online 中打开

br_peaks = [1 2 3 4 5 6 7];
lbr = numel(br_peaks);
points = repmat(br_peaks,lbr,1);
for iii = 1:lbr
    for jj = max(1,iii-3):max(0,iii-1)
       points(iii,jj) = points(iii,jj) - br_peaks(iii);
    end
    for jj = max(lbr-2,iii+1):min(lbr,iii+3)
       points(iii,jj) = points(iii,jj) - br_peaks(iii);
    end
end 
points
points = 7×7
     1     2     3     4     5     6     7
    -1     2     3     4     3     6     7
    -2    -1     3     4     2     3     7
    -3    -2    -1     4     1     2     3
     1    -3    -2    -1     5     1     2
     1     2    -3    -2    -1     6     1
     1     2     3    -3    -2    -1     7