Appending a row/column of different size to an array.
Recently, I came across this behaviour in Matlab and I am curious as to know why this happens.
a(1,:) = rand(4,1);
a(2,:) = rand(5,1);
This throws me Subscripted assignment dimension mismatch. error whereas
a(1,:) = rand(4,1);
a(2,1:5) = rand(5,1);
adjusts the array to the max column size and appends zero to the shorter ones.
My question is: Why the former code snippet doesn't do what the latter does(which seems very logical to me)? I don't see any reason as to why the former code snippet should work the way it does. Or am I missing something?
matlab
asked Nov 23 '18 at 10:15
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Recently, I came across this behaviour in Matlab and I am curious as to know why this happens.
a(1,:) = rand(4,1);
a(2,:) = rand(5,1);
This throws me Subscripted assignment dimension mismatch. error whereas
a(1,:) = rand(4,1);
a(2,1:5) = rand(5,1);
adjusts the array to the max column size and appends zero to the shorter ones.
My question is: Why the former code snippet doesn't do what the latter does(which seems very logical to me)? I don't see any reason as to why the former code snippet should work the way it does. Or am I missing something?
matlab
asked Nov 23 '18 at 10:15
Backspace
133
add a comment |
Recently, I came across this behaviour in Matlab and I am curious as to know why this happens.
a(1,:) = rand(4,1);
a(2,:) = rand(5,1);
This throws me Subscripted assignment dimension mismatch. error whereas
a(1,:) = rand(4,1);
a(2,1:5) = rand(5,1);
adjusts the array to the max column size and appends zero to the shorter ones.
My question is: Why the former code snippet doesn't do what the latter does(which seems very logical to me)? I don't see any reason as to why the former code snippet should work the way it does. Or am I missing something?
matlab
asked Nov 23 '18 at 10:15
Backspace
133
Recently, I came across this behaviour in Matlab and I am curious as to know why this happens.
a(1,:) = rand(4,1);
a(2,:) = rand(5,1);
This throws me Subscripted assignment dimension mismatch. error whereas
a(1,:) = rand(4,1);
a(2,1:5) = rand(5,1);
adjusts the array to the max column size and appends zero to the shorter ones.
My question is: Why the former code snippet doesn't do what the latter does(which seems very logical to me)? I don't see any reason as to why the former code snippet should work the way it does. Or am I missing something?
matlab
matlab
asked Nov 23 '18 at 10:15
Backspace
133
asked Nov 23 '18 at 10:15
Backspace
133
asked Nov 23 '18 at 10:15
Backspace
133
asked Nov 23 '18 at 10:15
Backspace
133
asked Nov 23 '18 at 10:15
Backspace
133
133
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add a comment |
1 Answer
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With a(2,:) = rand(5,1);, you are attempting to assign a 5x1 vector to a 4x1 matrix column. Hence the error.
With a(2,1:5) = rand(5,1);, you are explicitly referencing a 5th row, which tells the Matlab engine to expand the matrix accordingly before attempting the assignment operation. Hence, this will succeed.
The way I see it, trying to put 5 values into a 4 row vector likely comes from an error in the code, so the user has to explicitly state that this is what he intends to do. Of course, I can only infer on the intent of Mathworks developers when they specifiy the behavior of their language.
answered Nov 23 '18 at 11:16
Brice
1,357110
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1 Answer
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With a(2,:) = rand(5,1);, you are attempting to assign a 5x1 vector to a 4x1 matrix column. Hence the error.
With a(2,1:5) = rand(5,1);, you are explicitly referencing a 5th row, which tells the Matlab engine to expand the matrix accordingly before attempting the assignment operation. Hence, this will succeed.
The way I see it, trying to put 5 values into a 4 row vector likely comes from an error in the code, so the user has to explicitly state that this is what he intends to do. Of course, I can only infer on the intent of Mathworks developers when they specifiy the behavior of their language.
answered Nov 23 '18 at 11:16
Brice
1,357110
add a comment |
With a(2,:) = rand(5,1);, you are attempting to assign a 5x1 vector to a 4x1 matrix column. Hence the error.
With a(2,1:5) = rand(5,1);, you are explicitly referencing a 5th row, which tells the Matlab engine to expand the matrix accordingly before attempting the assignment operation. Hence, this will succeed.
The way I see it, trying to put 5 values into a 4 row vector likely comes from an error in the code, so the user has to explicitly state that this is what he intends to do. Of course, I can only infer on the intent of Mathworks developers when they specifiy the behavior of their language.
answered Nov 23 '18 at 11:16
Brice
1,357110
add a comment |
With a(2,:) = rand(5,1);, you are attempting to assign a 5x1 vector to a 4x1 matrix column. Hence the error.
With a(2,1:5) = rand(5,1);, you are explicitly referencing a 5th row, which tells the Matlab engine to expand the matrix accordingly before attempting the assignment operation. Hence, this will succeed.
The way I see it, trying to put 5 values into a 4 row vector likely comes from an error in the code, so the user has to explicitly state that this is what he intends to do. Of course, I can only infer on the intent of Mathworks developers when they specifiy the behavior of their language.
answered Nov 23 '18 at 11:16
Brice
1,357110
With a(2,:) = rand(5,1);, you are attempting to assign a 5x1 vector to a 4x1 matrix column. Hence the error.
With a(2,1:5) = rand(5,1);, you are explicitly referencing a 5th row, which tells the Matlab engine to expand the matrix accordingly before attempting the assignment operation. Hence, this will succeed.
The way I see it, trying to put 5 values into a 4 row vector likely comes from an error in the code, so the user has to explicitly state that this is what he intends to do. Of course, I can only infer on the intent of Mathworks developers when they specifiy the behavior of their language.
answered Nov 23 '18 at 11:16
Brice
1,357110
edited Nov 23 '18 at 11:28
answered Nov 23 '18 at 11:16
Brice
1,357110
answered Nov 23 '18 at 11:16
Brice
1,357110
answered Nov 23 '18 at 11:16
Brice
1,357110
1,357110
add a comment |
add a comment |
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