On Tue, Aug 21, 2012 at 5:51 PM, Martin Helm
<address@hidden> wrote:
Am 21.08.2012 14:15, schrieb vivek dogra:
>
>
> By neither increasing nor decreasing, i meant if it is unsorted.
> example:
>
> X = [ 2 1 2 3];
> Y = [ 2 1 3 4];
>
This was already ruled out by Ben's answer that in such a case the
vector will be sorted! So the only case which was left is the constant one.
So it means whenever X is unsorted, interp1 will always give the
"discontinuous interpolant" corresponding to increasing values of X. It
means it is hard coded in the function that it will always sort X in
increasing order. So, it is not symmetric. Why interp1 is favoring
right-continuous?
Now looking from the practical point of view let's say (because of some error) we have following data points:
X = [ 1 2 2 3];
Y = [ 1 2 10 4];
In this case because X is increasing, interp1 will consider value of 2 as 10.
which is of course incorrect.
In this case it will be better for
the user to do some pre-processing (as in whether to take the max.,
min., or the mean of 2 identical values)