Index exceeds matrix dimensions. where is mistake

Question

Sultan Mehmood 2019-7-4

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/470225-index-exceeds-matrix-dimensions-where-is-mistake

编辑： KALYAN ACHARJYA 2019-7-4

II=[14 23;44 15];

R=II(:)';

x=0.3;

p=0.343;

for n=2:4;

if x(n-1)>=0 & x(n-1)<=p

x(n)=x(n-1)/p;

else

x(n)=(1-x(n-1))/(1-p);

end

A=sort(x);

[A,T]=sort(x);

Y=R(T);

C=reshape(Y,[2,2]);

r = 3.8;

size = 4;

L(1)= 0.234;

for i=2:size

L(i) = r*L(i-1)*(1-L(i-1));

end

mm=min(L);

nn=max(L);

oo=nn-mm;

Z=uint8(8*((L-mm)/oo))+1;

%for i=1:9

%K(i)=mod((abs(L(i))-floor(abs(L(i))))*1e14,50);

%end

CC(1)=bitxor(mod(157,50),mod(Y(1)+Z(1),50));

for i=2:4

CC(i)=bitxor(mod(CC(i-1),50),mod(Y(i)+Z(i),50));

end

X=[12 13 13 14;12 15 16 34;17 18 19 13 ;12 34 32 31];

sX=size(X);

[cA,cH,cV,cD] = dwt2(X,'db4');

subplot(2,2,1);

imagesc(cA);

colormap gray;

title('Approximation');

subplot(2,2,2);

imagesc(cH);

colormap gray;

title('Horizontal');

subplot(2,2,3);

imagesc(cV);

colormap gray;

title('Vertical');

subplot(2,2,4);

imagesc(cD);

colormap gray;

title('Diagonal');

for m=1:2;

for n=1:2;

VV(m,n)=floor(C(m,n)/10);

DD(m,n)=mod(C(m,n),10);

end

S = idwt2(cA,cH,VV,DD,'db4',sX);

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Answer 1

Raj 2019-7-4

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https://ww2.mathworks.cn/matlabcentral/answers/470225-index-exceeds-matrix-dimensions-where-is-mistake#answer_381945

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In line number 17 you have defined

size = 4;

which you are using in your 'for' loop at line 19. This variable is clashing with Matlab inbuilt function 'size' which you are trying to use at line 34. Hence you are getting the error. Change the variable name.

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KALYAN ACHARJYA 2019-7-4

编辑：KALYAN ACHARJYA 2019-7-4

在 MATLAB Online 中打开

Yes @Raj

Size variable name (line 7) is confliting with inbuilt function name.

II=[14 23;44 15];
R=II(:)';
x=0.3;
p=0.343;
for n=2:4;
if x(n-1)>=0 & x(n-1)<=p
 x(n)=x(n-1)/p;
else
 x(n)=(1-x(n-1))/(1-p);
end
end
A=sort(x);
[A,T]=sort(x);
Y=R(T);
C=reshape(Y,[2,2]);
r = 3.8;
size1 = 4;  %%% Issue was here, I have change the variable name size to size1
L(1)= 0.234;
for i=2:size1
   L(i) = r*L(i-1)*(1-L(i-1));
end
mm=min(L);
nn=max(L);
oo=nn-mm;
Z=uint8(8*((L-mm)/oo))+1;
%for i=1:9
%K(i)=mod((abs(L(i))-floor(abs(L(i))))*1e14,50);
%end
CC(1)=bitxor(mod(157,50),mod(Y(1)+Z(1),50));
for i=2:4
CC(i)=bitxor(mod(CC(i-1),50),mod(Y(i)+Z(i),50));
end 
X=[12 13 13 14;12 15 16 34;17 18 19 13;12 34 32 31];
sX=size(X);
[cA,cH,cV,cD] = dwt2(X,'db4');
subplot(2,2,1);
imagesc(cA);
colormap gray;
title('Approximation');
subplot(2,2,2);
imagesc(cH);
colormap gray;
title('Horizontal');
subplot(2,2,3);
imagesc(cV);
colormap gray;
title('Vertical');
subplot(2,2,4);
imagesc(cD);
colormap gray;
title('Diagonal');
for m=1:2;
for n=1:2;
  VV(m,n)=floor(C(m,n)/10);
  DD(m,n)=mod(C(m,n),10);
end
end
S = idwt2(cA,cH,VV,DD,'db4',sX);

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Answer 2

Aiswarya Subramanian 2019-7-4

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https://ww2.mathworks.cn/matlabcentral/answers/470225-index-exceeds-matrix-dimensions-where-is-mistake#answer_381944

Hello Sultan,

Could you send the error message? In your code you have initialised x = 0.3, which is a scalar. So x(n-1) will give rise to an error.

Also, after your for loop statement, you have put a semi colon (as shown below)

>> for n=2:4;

Hope this helps :)

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Raj 2019-7-4

x=0.3 is equivalent to x(1)=0.3 which is what is used while indexing x(n-1) for the first time. So no issue there. It will not give error. Also, semicolon after 'for' loop will not give any error.