concatenating more values on a matrix

Question

Alexandru Miculescu 2015-3-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/184315-concatenating-more-values-on-a-matrix

编辑： Stephen23 2015-3-21

Hi everyone! I've been struggling with a simple problem for a while but i could not figure it out how to do it. What i want to do is that if it happens to be the same value more then once on the first column is to eliminate the others and add their second column together. For the example in the picture i want:

6 - 0.03;

8 - 0.05;

5 - 0.06;

3 - 0.03;

if true
  % v = fix(10*rand(10))
heads = 1:10;
probab = 1:10;
count = 0;
for i = 1:10
  heads(i) = v(i);
  for j = 1:10
      if ( v(i,j) == heads(i) )
         count = count + 1;
      end
  end
  probab(i) = count;
  count = 0;    
end
X = vertcat(heads, probab/100)
end

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Stephen23 2015-3-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/184315-concatenating-more-values-on-a-matrix#answer_172170

编辑：Stephen23 2015-3-21

在 MATLAB Online 中打开

You can do this quite easily using unique and accumarray. In fact solving this kind of problem is exactly what accumarray is intended for:

>> A = [6,3,8,5,3,9,8,5,6,5;0.01,0.02,0.03,0.01,0.01,0.03,0.02,0.02,0.02,0.03];
>> [B,~,idx] = unique(A(1,:));
>> [B.',accumarray(idx(:),A(2,:))]
ans =
          3         0.03
          5         0.06
          6         0.03
          8         0.05
          9         0.03

If you have a newer MATLAB version you can use the 'stable' option as well, which might give you the output order you want:

>> [B,~,idx] = unique(A(1,:),'stable');
>> [B.',accumarray(idx(:),A(2,:))]
ans =
          6         0.03
          3         0.03
          8         0.05
          5         0.06
          9         0.03