Simple rounding numbers in a matrix

Question

André Pacheco 2012-12-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/57190-simple-rounding-numbers-in-a-matrix

采纳的回答： Azzi Abdelmalek

Hello,

I have a matrix that consist in a bunch of numbers. Por exemple matrix(a)=

1.46101448605678 0.124416958027372

0.00918754579219433 -0.0655659591723838

0.549665183459168 0.218046503150596

What i want to do is make something that can round my numbers to 0, -1 and 1. If the number in the matrix is <-0,5 it should put -1 if it is bigger than 0.5 it should put 1. And the other numbers put into 0.

Thanks in advance.

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

Azzi Abdelmalek 2012-12-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/57190-simple-rounding-numbers-in-a-matrix#answer_69172

编辑：Azzi Abdelmalek 2012-12-21

在 MATLAB Online 中打开

A=2*rand(5)-1  % Example
A(A<-0.5)=-1;
A(A>0.5)=1;
A(-0.5<A  & A<0.5)=0

2 个评论
显示无隐藏无

André Pacheco 2012-12-21

It works, but it changes the structure of my matrix. Don't know why. My matrix is a 2x5 and after that it changes to a 1x10. Do you know why?

André Pacheco 2012-12-21

Oh, i solved this initiating the new matrix with zeros.

请先登录，再进行评论。

Answer 2

Roger Stafford 2012-12-21

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/57190-simple-rounding-numbers-in-a-matrix#answer_69173

编辑：Roger Stafford 2012-12-21

在 MATLAB Online 中打开

b = (a>.5)-(a<-.5);

Roger Stafford

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。

Answer 3

Image Analyst 2012-12-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/57190-simple-rounding-numbers-in-a-matrix#answer_69176

在 MATLAB Online 中打开

Andre, if you have the Image Processing Toolbox, you can quantize your array with the imquantize function in a single line of code:

m=[...
1.46101448605678 0.124416958027372
0.00918754579219433 -0.0655659591723838
0.549665183459168 0.218046503150596]
m_quantized = imquantize(m, [-0.5, 0.5])-2

In the command window:

m =
          1.46101448605678         0.124416958027372
       0.00918754579219433       -0.0655659591723838
         0.549665183459168         0.218046503150596
m_quantized =
     1     0
     0     0
     1     0

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。

Answer 4

Shaun VanWeelden 2012-12-22

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/57190-simple-rounding-numbers-in-a-matrix#answer_69195

编辑：Shaun VanWeelden 2012-12-22

在 MATLAB Online 中打开

Not to assume anything, but as a tutor for MATLAB, I have seen this question many, many times. If you are starting out in MATLAB, a good and easy approach is to use for loops and an if-else statement

[rows columns]=size(yourMatrix)

 for i=1:rows
  for j=1:columns
     if yourMatrix(i,j)>.5
        yourMatrix(i,j)=1
     elseif yourMatrix(i,j)<-.5
        yourMatrix(i,j)=-1
     else %its between those two
        yourMatrix(i,j)=0
     end
  end
end

I hope that helps you and anyone else, let me know if you have more questions :)

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Image Analyst 2012-12-22

Do your students then tend to use this loop based approach even after they've been shown the vectorized approach? Or do they switch over immediately once they learn the vectorized approach after this? I've seen people use loops for matrices that are millions of elements, even though they've been using MATLAB for months or years, when they could have used a faster vectorized approach instead.

请先登录，再进行评论。