Nested loop problem !

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Susan
Susan 2011-7-26
Hey every1.. I am working on arrays and I am finding it quite confusing and slowly getting it.. I want to replace the content of a double array with another double array and I belive since is double I should use a nested loop but I am not sure how it works?? I tried several of ways which is below but the content is not being replaced.. I keep checking it from the matlab work space .. My code is below.. the size is 2x100 and in matlab workspace is two rows.. with my code instead of replacing the content it adds extra row to array b?? I want to start the replace from a(3,1) with b(1,1). a(4,1) with b(2,1) etc then when it finishes this row the second row etc
a(x;y)
b(s,f)
d = 2;
for i=3,j=1:100
a(i,j) = b(i -d,j);
i = i+1;
j = j+1
end
Thanks in advance !!
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Nathan Greco
Nathan Greco 2011-7-27
Note that if your arrays are size 2x100, then you should be indexing them as "a(1,3) with b(1,1). a(1,4) with b(1,2)". (How can you reach a(4,1) if there are only two rows in a? (Note that indexing goes a(row,column))

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Nathan Greco
Nathan Greco 2011-7-26
Will this do what you are looking for:
EDIT:
a(:,3:end) = b(:,1:end-2);
OR, if you really wanted a for loop:
d = 2;
for i=1:100-d
a(:,i+2) = b(:,i);
end
-Nathan
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Nathan Greco
Nathan Greco 2011-7-27
Based on "test" data that I am using that just use the dimensions you provided (2x100), my method seems to work. I used a = ones(2,100); and b = rand(2,100);
The result from a(:,3:end) = b(:,1:end-2); (this line alone, no for loop involved) turns a into a 2x100 (same size) array, with a(1:2,1:2) remaining ones, and the rest of a having been replaced with b.
Susan
Susan 2011-7-27
Yeah, It worked perfectly fine.. was looking at the columns but read your comment that it starts with rows.. Thanks alot for your help.. Now I can carry on and learning more about the loops and arrays :)

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更多回答（1 个）

Andrei Bobrov
Andrei Bobrov 2011-7-27
eg:
a = randi(15,4,10) % array 4x10
b = randi(20,2,10) %array 2x10
a(3:end,:)=b
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Susan
Susan 2011-7-27
Yeah thats exactly what I would like to do!!
Nathan Greco
Nathan Greco 2011-7-27
And, sorry for mixing up terminology, the "rows" should actually be "columns".

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