Keep getting "Index exceeds number of array elements (1)" message

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Reem Gawish
Reem Gawish 2020-4-21
评论： Reem Gawish 2020-4-21
Hi, I have this code below, which works when I simplify the code to simply add to either x or y arrays, but doesn't work when I'm doing both, can anyone help me figure out why this may be? I'm being told from the error message that there's something wrong with "x(t)=x(t-1)-1;"
x(1)=0;
y(1)=0;
c=clock;
z=c(1,6)*1000;
rand('seed',z);
for i=1:50
r(i)=floor((3-1)*rand(1)+1);
r2(i)=floor((5-1)*rand(1)+1);
end
for t=2:50
if r(t)==1
if mod(r2(t),2)==0
x(t)=x(t-1)+1;
else
x(t)=x(t-1)-1;
end
end
if r(t)==2
if mod(r2(t),2)==0
y(t)=y(t-1)+1;
else
y(t)=y(t-1)-1;
end
end
end
disp(x)
disp(y)
  2 个评论
Toey
Toey 2020-4-21
编辑：Toey 2020-4-21
Hi Reem,
In your code, x & y only increase their sizes when r(t)==1 and r(t)==2, but your index t increases by 1 every loop. This is when there's mismatch between indexing and the size of x,y.
To fix the issue, you can preallocate x,y in the beginning of your code
x=zeros(50,1); y=zeros(50,1);
or having x(t) =0 in the else statement when r(t)==1 isn't met.

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采纳的回答

Sriram Tadavarty
Sriram Tadavarty 2020-4-21
Hi Reem,
Make minor modification to the code to avoid that error as shown below:
x(1)=0;
y(1)=0;
c=clock;
z=c(1,6)*1000;
rand('seed',z);
for i=1:50
r(i)=floor((3-1)*rand(1)+1);
r2(i)=floor((5-1)*rand(1)+1);
end
for t=2:50
if r(t)==1
if mod(r2(t),2)==0
x(t)=x(t-1)+1;
else
x(t)=x(t-1)-1;
end
else
x(t) = 0; % Added this to ensure that value is stored as zero, when r(t) is not equal to 1
end
if r(t)==2
if mod(r2(t),2)==0
y(t)=y(t-1)+1;
else
y(t)=y(t-1)-1;
end
else
y(t)=0; % Added this to ensure that value is stored as zero, when r(t) is not equal to 2
end
end
disp(x)
disp(y)
Hope this helps.
Regards,
Sriram

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