Question

matlab如何将矩阵中处于某一范围的值替换为特定值

例如有个矩阵A=[1,2,1,2;1,3,4,5;2,4,3,1]我想把小于等于2的值变为0，大于2小于等于4的值变为1，大于4的值变为2

Answer 1

两种方式
1，不用循环
代码：
A=[-5, -4, -3, -2; -1, 0, 1, 2; 3, 4, 5, 6];
%a<=-2 ---->0; -2<a<=3--->1; a>3------->2.
sizeA = size(A);
a1 = zeros(sizeA);
a2 = a1;
a3 = a1;
a1(A <= -2) = 0;
a2(A > -2 & A <= 3) = 1;
a3(A > 3) = 2;
B = a1 + a2 + a3

2，用盯启循岩知环凯枣如
代码：
A=[-5 -4 -3 -2;-1 0 1 2;3 4 5 6]
for ii=1:3
for jj=1:4
if A(ii,jj)<=-2
A(ii,jj)=0;
elseif A(ii,jj)>-2&&A(ii,jj)<=3
A(ii,jj)=1;
elseif A(ii,jj)>3
A(ii,jj)=2;
end
end
end
A

Answer 2

两种方式
1，不用循环
代码：
A=[-5,
-4,
-3,
-2;
-1,
0,
1,
2;
3,
4,
5,
6];
%a<答稿塌=-2
---->0;
-2<a<=3--->1;
a>3------->2.
sizeA
=
size(A);
a1
=
zeros(sizeA);
a2
=
a1;
a3
=
a1;
a1(A
<=
-2)
=
0;
a2(A
>
-2
&
A
<=
3)
=
1;
a3(A
>
3)
=
2;
B
=
a1
+
a2
+
a3
2，用循环
代清圆码：
A=[-5
-4
-3
-2;-1
0
1
2;3
4
5
6]
for
ii=1:3
for
jj=1:4
if
A(ii,jj)<=-2
A(ii,jj)=0;
elseif
A(ii,jj)>-2&&A(ii,jj)<敬改=3
A(ii,jj)=1;
elseif
A(ii,jj)>3
A(ii,jj)=2;
end
end
end
A

Answer 3

A=[1,2,1,2;1,3,4,5;2,4,3,1];
for i=1:3
for j=1:4
if (A(i,j)<=2)
A(i,j)=0;
end
if (A(i,j)>2)&&(A(i,j)<=4)
A(i,j)=1;
end
if A(i,j)>4
A(i,j)=2;
end
end
end
A

Answer 4

三句就可以了
A(A<=2) = 0;
A(A>2 & A<=4) = 1;
A(A>4) = 2;