is it possible to....

[greenflame]

Is it possible to swap two elements of an array? for example like swap
rows in the matrix:

[1 5 7 3]
[2 6 2 5]
[6 5 1 7]

where I make a matrix as an array of arrays. where the inner arrays are
the rows of the matrix. so the above could be coded as:

A = [
[1,5,7,3],
[2,6,2,6],
[6,5,1,7]
];

[RobG]

Re: is it possible to....

greenflame wrote:[color=blue]
> Is it possible to swap two elements of an array? for example like swap
> rows in the matrix:
>
> [1 5 7 3]
> [2 6 2 5]
> [6 5 1 7]
>
> where I make a matrix as an array of arrays. where the inner arrays are
> the rows of the matrix. so the above could be coded as:
>
> A = [
> [1,5,7,3],
> [2,6,2,6],
> [6,5,1,7]
> ];
>[/color]

Below is some commented code with alerts to show what is happening
- you can safely remove the alerts.

You may want to check that A, A[r1] and A[r2] actually exist before
trying to swap them.


function swapRows( A, r1, r2 ){
var i = A.length;
alert(A.join('\ n'));
A[i] = A[r1]; // Copy r1 to an extra element
alert(A.join('\ n'));
A[r1] = A[r2]; // Copy r2 into r1
alert(A.join('\ n'));
A[r2] = A[i]; // Put remembered r1 into r2
alert(A.join('\ n'));
delete A[i]; // Remove copy of r1
alert(A.join('\ n'));
}

B = [
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
];

swapRows( B, 0, 2 );


--
Rob

[RobG]

Re: is it possible to....

RobG wrote:
[...][color=blue]
> function swapRows( A, r1, r2 ){
> var i = A.length;
> alert(A.join('\ n'));
> A[i] = A[r1]; // Copy r1 to an extra element
> alert(A.join('\ n'));
> A[r1] = A[r2]; // Copy r2 into r1
> alert(A.join('\ n'));
> A[r2] = A[i]; // Put remembered r1 into r2
> alert(A.join('\ n'));
> delete A[i]; // Remove copy of r1
> alert(A.join('\ n'));[/color]

Forgot to mention that as A is just a reference to B, whatever we do
to A also happens to B, so:

alert(B.join('\ n'));

shows that B now has its rows swapped.

[...]


--
Rob

[Jc]

Re: is it possible to....

greenflame wrote:[color=blue]
> Is it possible to swap two elements of an array?[/color]

Sure, array's are read/write, so just use a temporary var while
swapping so you don't lose one of the array items.

Example:

<script>
var a1 = [1,2,3];
var a2 = [4,5,6];
var aMatrix = [a1, a2];
alert("before swap:\n"+aMatri x.join("\n"));

var aTemp = aMatrix[0];
aMatrix[0] = aMatrix[1];
aMatrix[1] = aTemp;
alert("after swap:\n"+aMatri x.join("\n"));
</script>

[Lee]

Re: is it possible to....

greenflame said:[color=blue]
>
>Is it possible to swap two elements of an array? for example like swap
>rows in the matrix:
>
>[1 5 7 3]
>[2 6 2 5]
>[6 5 1 7]
>
>where I make a matrix as an array of arrays. where the inner arrays are
>the rows of the matrix. so the above could be coded as:
>
>A = [
>[1,5,7,3],
>[2,6,2,6],
>[6,5,1,7]
>];[/color]

Certainly.
But I can't be more specific without more than a "for example".

[greenflame]

Re: is it possible to....

I had a problem with the part where you remove the last row. It didnt
remove it, well yes but no. Anyway I fixed it by using the pop command.
Thanks!