Simple rounding numbers in a matrix
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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.
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Réponse acceptée
Azzi Abdelmalek
le 21 Déc 2012
Modifié(e) : Azzi Abdelmalek
le 21 Déc 2012
A=2*rand(5)-1 % Example
A(A<-0.5)=-1;
A(A>0.5)=1;
A(-0.5<A & A<0.5)=0
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Plus de réponses (3)
Roger Stafford
le 21 Déc 2012
Modifié(e) : Roger Stafford
le 21 Déc 2012
b = (a>.5)-(a<-.5);
Roger Stafford
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Image Analyst
le 21 Déc 2012
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
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Shaun VanWeelden
le 22 Déc 2012
Modifié(e) : Shaun VanWeelden
le 22 Déc 2012
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 commentaire
Image Analyst
le 22 Déc 2012
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.
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