executing a loop most probably while

Question

Busy Bee 2018-1-16

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/377409-executing-a-loop-most-probably-while

编辑： Guillaume 2018-1-16

I have created a function which groups a vast data. Here, for simplicity, I have used 20 data points. group(x,y) creates the required group (g1) and the next 'for' loop removes the elements of this group to create a new dataset. Again the group(x,y) creates the next group(g2) and the initial dataset is modified. I want to create a loop which will execute this till the dataset has zero elements,i.e. all the elements are grouped with group numbers,g1,g2 etc. I have tried to use while loop but I cannot change the group names, hence the error. Any help will be appreciated.

x = gallery('uniformdata',20,1,1);
y = gallery('uniformdata',20,1,1);
group(x,y);
g1=ans
for i=1:length(g1)
    x(any(x==g1(i,1),2),:)=[];
    y(any(y==g1(i,2),2),:)=[];
end
group(x,y);
g2=ans
for i=1:length(g2)
    x(any(x==g2(i,1),2),:)=[];
    y(any(y==g2(i,2),2),:)=[];
end

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Stephen23 2018-1-16

@Busy Bee:

Why do you not return any output from group ?
Do NOT use ans as a variable name.
Do not try to magically generate variable names g1, g2, etc:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Just use simpler and much more efficient indexing.

Busy Bee 2018-1-16

在 MATLAB Online 中打开

this is the answer i want

g1 =
1996    0.0736
4428    0.0015
8407    0.0159
9102    0.3281
9528    0.4493
9539    0.9641
g2 =
3759    0.1164
5982    0.0765
7041    0.2088
8368    0.2609
8986    0.5779
g3 =
3068    0.4931
5187    0.3469
5383    0.4436
7153    0.6566
g4 =
4290    0.4946
5253    0.8889
g5 =
0222    0.9105
3031    0.9285
g6 =
0345    0.9509

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Answer 1

Guillaume 2018-1-16

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/377409-executing-a-loop-most-probably-while#answer_300363

编辑：Guillaume 2018-1-16

在 MATLAB Online 中打开

First, some important notes

group(x, y);
g = ans;

Do not do this! This is just a more complicated and confusing way of simply doing

g = group(x, y);

Secondly, you create x and y as column vectors, but then have

x(any(x == g(i,1), 2), :) = [];
y(any(x == g(i,1), 2), :) = [];

which is designed for x and y matrices. If x and y are indeed vector then the above can be reduced simply to

x(x == g(i, 1)) = [];
y(y == g(i, 2)) = [];

In addition the i loop can be entirely removed, for x, y matrices:

x(any(ismember(x, g(:, 1)), 2)) == [];
y(any(ismember(y, g(:, 2)), 2)) == [];

and for x, y vectors simply:

x(ismember(x, g(:, 1))) = [];
y(ismember(y, g(:, 2))) = [];

Now to answer your question, first do not number variables, see Stephen's comment. Instead create a cell array that can easily be indexed:

x = gallery('uniformdata',20,1,1);
y = gallery('uniformdata',20,1,1);
g = {}; %better variable name required
count = 0;
while ~isempty(x)
   count = count + 1;
   g{count} = group(x, y);
   x(ismember(x, g{count}(:, 1))) = [];
   y(ismember(y, g{count}(:, 2))) = [];
end