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Re: Fractional SHIFT [message #28348 is a reply to message #28345]

Mon, 03 December 2001 13:34

tam
Messages: 48
Registered: February 2000

Member

For 1-D you could try the interpol function rather than interpolate...
It seems to extrapolate beyond the grid which seems to be what you want.
You need to specify both x and y values. I.e., you'll

new = INTERPOL(xvals, yvals, xvalues_to_interpolate_at)

Personally I've always found the behavior of interpolate to be
more useful, but typically I'm worried about going over the edge
of an image....

Tom McGlynn

trouble wrote:
>
> Hi,
>
> Does anyone have a method for doing non-integer shifts ? Interpolate
> doesn't wrap in the way SHIFT does and my hack (based on MOD) is a bit
> dodgy.
>
> To shift orig by 1.5 pixels:
>
> orig = FINDGEN(10)
>
> index = FINDGEN(10)
> delta = 1.5
> index2 = (index+delta) MOD 10
>
> new = INTERPOLATE(orig,index2,/GRID)
>
> PRINT,new
>
> 1.50000 2.50000 3.50000 4.50000 5.50000
> 6.50000
> 7.50000 8.50000 9.00000 0.500000
>
> The 2nd last element of new is wrong (should be 9.5).
>
> Does anyone know a robust way ?
>
> Ciao.

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[Message index]

		Re: Fractional SHIFT By: the_cacc on Tue, 04 December 2001 05:34
		Re: Fractional SHIFT By: Mark Rivers on Mon, 03 December 2001 19:55
		Re: Fractional SHIFT By: tam on Mon, 03 December 2001 13:34
		Re: Fractional SHIFT By: Ralf Flicker on Mon, 03 December 2001 13:10

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