How to pick group sum values from an array

Question

Poorna Durga Geesupalli 2022-11-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1865683-how-to-pick-group-sum-values-from-an-array

评论： William Rose 2022-12-2

采纳的回答： William Rose

How can I do the group sum in an array.

X=[1111100000000010000000100011100011111];

In this X array, I wanna group the values where index 1 occus for 3 or more consecutive cells.

Answer like X1=sum(5+1+1+3+5)=15;

But I need X2=groupsum[5 3 5];

How can I do this.

Thanks,

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Stephen23 2022-12-2

在 MATLAB Online 中打开

X = '1111100000000010000000100011100011111';
[S,E] = regexp(X,'1{3,}');
N = E-S+1
N = 1×3
     5     3     5

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Answer 1

William Rose 2022-11-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1865683-how-to-pick-group-sum-values-from-an-array#answer_1114448

编辑：William Rose 2022-11-28

在 MATLAB Online 中打开

@Poorna Durga Geesupalli,

[edit: correct a typo in one of the comment lines in the code, fix indenting, add comments]

Xs='1111100000000010000000100011100011111';
%% Convert string of digits to array of numbers
X=zeros(1,length(Xs)); 
for i=1:length(X),X(i)=str2num(Xs(i)); end
%% Process the array, looking for groups of 3 or more consecutive 1's
i=3;        % i=current position in vector X
k=1;        % k=current position in vector X2
X2=[];
while i<=length(X)
    j=i-2;
    c=1;   %c=1 indicates we should check X1 
    while c && i<=length(X)
        X1=sum(X(j:i));
        if X1<(i-j+1)
            c=0;  %There is at least one "0" in the group, so move one
        end
        i=i+1;
    end
    if X1>=3
        X2=[X2,X1];  %append X1 to X2
        k=k+1;
    end
end
%% Display result
fprintf('X2 =');disp(X2)
X2 =     5     3     5

Try it. Good luck.

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Stephen23 2022-12-2

编辑：Stephen23 2022-12-2

在 MATLAB Online 中打开

Calling STR2NUM inside a loop in order to convert from char to numeric is very inefficient.

Two simple MATLAB approaches:

X = '1111100000000010000000100011100011111';
X-'0'
ans = 1×37
     1     1     1     1     1     0     0     0     0     0     0     0     0     0     1     0     0     0     0     0     0     0     1     0     0     0     1     1     1     0
sscanf(X,'%1u',[1,Inf])
ans = 1×37
     1     1     1     1     1     0     0     0     0     0     0     0     0     0     1     0     0     0     0     0     0     0     1     0     0     0     1     1     1     0

William Rose 2022-12-2

THank you @Stephen23. Those are nice to know about.

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Answer 2

chrisw23 2022-11-28

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https://ww2.mathworks.cn/matlabcentral/answers/1865683-how-to-pick-group-sum-values-from-an-array#answer_1114358

编辑：chrisw23 2022-11-28

X=[1 1 1 1 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 1 1 1 0 0 0 1 1 1 1 1];

xStr = string(X).join("");

pat = asManyOfPattern("1",3); % group of at least 3 times "1"

matchVec = xStr.extract(pat);

count = matchVec.join.strlength;

...a step by step example using string functions for this special case

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Answer 3

Vilém Frynta 2022-11-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1865683-how-to-pick-group-sum-values-from-an-array#answer_1114363

在 MATLAB Online 中打开

I tried this: (converting into text, deleting zeros, then finding strings of ones and checking their length)

but I have to go. I might come back later to finish this, but you get the idea. Hope I helped.

x = [1,1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,1,1,1,0,0,0,1,1,1,1,1];
xTxt = num2str(x)
xTxt = '1  1  1  1  1  0  0  0  0  0  0  0  0  0  1  0  0  0  0  0  0  0  1  0  0  0  1  1  1  0  0  0  1  1  1  1  1'
a = strsplit(xTxt,"0")
a = 1×23 cell array
    {'1  1  1  1  1  '}    {'  '}    {'  '}    {'  '}    {'  '}    {'  '}    {'  '}    {'  '}    {'  '}    {'  1  '}    {'  '}    {'  '}    {'  '}    {'  '}    {'  '}    {'  '}    {'  1  '}    {'  '}    {'  '}    {'  1  1  1  '}    {'  '}    {'  '}    {'  1  1  1  1  1'}