For loop question with matrix

Question

Gko K 2019-3-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/451926-for-loop-question-with-matrix

评论： Gko K 2019-3-25

I have a matrix as below called A (60x3 double)

A = [10           3.5          -34.66
           3.5          -35.6
           3.5          -31.43
           3.5          -29.04
           3.5          -27.81
           3.5          -26.59
           3.5          -23.69
           3.5          -16.47
           3.5          2.94
           3.5          24.03
           3.5          25.86
           3.5          35.98
           3.5          55.89
           3.5          91.82
           3.5          101.5
           3.5          -63.5
           3.5          -67.03
           3.5          -72.58
           3.5          -80.98
           3.5          -85.91
           3.5          -63.15
           3.5          -20.23
           3.5          -19.92
           3.5          -20.05
           3.5          -19.69
           3.5          -13.96
           3.5          11.57
           3.5          30.76
           3.5          63.36
           3.5          99.82
           3.5          107.13
         3.5          -47.09
           3.5          -61.25
           3.5          -61.89
           3.5          -63.07
           3.5          -65.29
           3.5          -69.63
           3.5          -76.96
           3.5          -84.92
           3.5          -80.39
           3.5          -57.89]

I want to sum column 2 values until column 1 value is 1. I mean first sum must be on row 1 to row 10, and 2nd sum must be on row 15 to row 20, 3rd sum must be on row 21 to row 26 etc.

How can i do that with using for loop or another way?

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Adam Danz 2019-3-23

在 MATLAB Online 中打开

The number 1 is in the following rows of column 1:

>> find(A(:,1)==1)
ans =
    10
    15
    21
    28
    31
    41

so I'm having trouble figuring out what rule you're using to select row numbers.

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Answer 1

Walter Roberson 2019-3-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/451926-for-loop-question-with-matrix#answer_367013

在 MATLAB Online 中打开

locs = [find(A(:,1)==1); size(A,1)+1];
tsum = cumsum([0;A(:,2)]);
output = tsum(locs(2:end)) - tsum(locs(1:end-1));

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Gko K 2019-3-23

编辑：Gko K 2019-3-23

在 MATLAB Online 中打开

Thank you friend.

I want to do something like this

a=[10	3	-3.04
9	3	3.4
8	3	11.5
7	3	16.5
6	3	20.45
5	3	25.86
4	3	35.98
3	3	55.89
2	3	91.82
1	3	101.5]
b=a(:,1);
c=a(:,2);
vd=a(:,3);
ht=sum(c);
for i=1:length(b)
if b(i)==1
h(i)=ht;
else
h(i)=ht-b(i+1)*c(i);
end
end
h=h'
hw3=ht/3
hwt3=ht-hw3
vv=max(vd)
vv05=vv/2
for ii=1:length(vd)
if vd(ii)<vv05
v(ii)=vv05
elseif vd(ii)>=vv05 
v(ii)=vd(ii)
end
end
v=v'
for j=1:length(b)
if h(j)>=hwt3 && v(j)>=0.5*vv
ve(j)=v(j);
elseif h(j)>=hwt3 && v(j)<0.5*vv
ve(j)=0.5*vv;
elseif h(j)<hwt3 && v(j)>=0.5*vv
ve(j)=v(j);
%%ve(j)=interp1(h(j),v(j),h(j));%%
elseif h(j)<hwt3 && v(j)<0.5*vv
ve(j)=0.5*vv;
end
end
ve=ve'

here is only one matrix. but i have a bigger matrix as below

a= [10           3.5          -34.66
           3.5          -35.6
           3.5          -31.43
           3.5          -29.04
           3.5          -27.81
           3.5          -26.59
           3.5          -23.69
           3.5          -16.47
           3.5          2.94
           3.5          24.03
           3.5          25.86
           3.5          35.98
           3.5          55.89
           3.5          91.82
           3.5          101.5
           3.5          -63.5
           3.5          -67.03
           3.5          -72.58
           3.5          -80.98
           3.5          -85.91
           3.5          -63.15
           3.5          -20.23
           3.5          -19.92
           3.5          -20.05
           3.5          -19.69
           3.5          -13.96
           3.5          11.57
           3.5          30.76
           3.5          63.36
           3.5          99.82
           3.5          107.13
         3.5          -47.09
           3.5          -61.25
           3.5          -61.89
           3.5          -63.07
           3.5          -65.29
           3.5          -69.63
           3.5          -76.96
           3.5          -84.92
           3.5          -80.39
           3.5          -57.89]

I want to run my code until i reach the value=1 on column 1. After this point i want to run again until i reach the value=1.......

In this big matrix i should have 6 matrices to run the code. How can i do that

Adam Danz 2019-3-24

Yeah, that was unclear to me from the beginning.

Gko K 2019-3-24

编辑：Gko K 2019-3-24

Ok, thank you both, Sorry if i make you busy.

I have analysis results which are in a big excel table.

I want to split matrix as i show below:

My code runs true if i have 1 matrix. But i have a big table as shown in the pic.I want to run code for matrix 1 then matrix 2 then matrix 3 then matrix 4 then matrix 5 then matrix....n.

If you dont want to help no problem. Thanks for your previous helps friends.

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Answer 2

Adam Danz 2019-3-24

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/451926-for-loop-question-with-matrix#answer_367084

编辑：Adam Danz 2019-3-24

在 MATLAB Online 中打开

"I want to sum column 2 values until column 1 value is 1."

With your input matrix "A", 's' is the sum of column 2 for each group.

% Create group numbers for each row
rowGroups = cumsum([0;A(1:end-1,1)] == 1)+1; 
% Calculate sum of col 2 for each group
s = splitapply(@sum, A(:,2), rowGroups)

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Adam Danz 2019-3-24

We've all been there.

Gko K 2019-3-25

Thank you

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For loop question with matrix

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