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Re: Interpolation [message #59871 is a reply to message #2184]

Mon, 14 April 2008 13:13

tarequeaziz
Messages: 20
Registered: November 2007

Junior Member

On Apr 14, 11:34 am, Spon <christoph.b...@gmail.com> wrote:
> On Apr 13, 1:56 am, tarequea...@gmail.com wrote:
>
>> Step one: Real data in a XY frame
>> Step two: 'Design a new xy frame, say X'Y' frame, whose values are
>> generated from a chosen r_vec and theta_vec.
>> Step 3: Now interpolate from XY to X'Y'.
>
>> Tareque
>
> Hi Tareque,
>
> I'm guessing you know whereabouts your small frame is, within your big
> frame, right?
> So, if you take your big normal (x'y') frame, your small frame can be
> defined by two points,
> bottom-left and top-right - let's call them (b,l) & (t,r) - in terms
> of x'y' grid co-oords.
>
> -----
> ; Once you've worked out where these two points are, you can use
> CONGRID on your xy dataset:
> tempx = r - l ; How many data points of the x'y' grid does the xy grid
> span
> tempy = t - b ; in each dimension?
>
> ; interpolate to new sub-grid
> newdata = congrid(data, tempx, tempy)
>
> ; Your x'y' frame co-ordinates for this data are
> newx = l + lindgen(tempx)
> newy = b + lindgen(tempy)
>
> ; (this bit is just array juggling to avoid for loops)
> newx = rebin(newx,tempx,tempy)
> newy = rebin(reform(newy,1,tempy),tempx,tempy)
> newx = reform(newx,n_elements(newx))
> newy = reform(newy,n_elements(newy))
>
> ; x'y' co-ordinates for ever datapoint in 'newdata'
> xycoords = transpose([[newx],[newy]])
>
> ; so your new data should be at r/theta co-ordinates defined by:
> polarcoords = cv_coord(from_rect = xycoords, /to_polar)
> -----
>
> I've assumed that your big circle is centered on the origin.
> I've also assumed your small circle is in the upper-right quadrant of
> your large circle here,
> so I don't have to wrap my mind around minus-signs and the like...
>
> I hope this helps and that I've understood your question
> correctly. :-)
>
> Regards,
> Chris

Hi Chris,

Thank you so much for getting back at this.
Without your permission I sent a picture of my set up. Hope that will
be able to shed some light on it.

Once again, much appreciated!

Best,
Tareque

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[Message index]

		Interpolation By: jun on Thu, 02 June 1994 10:44
		Re: Interpolation By: stl on Fri, 03 June 1994 01:14
		Re: Interpolation By: tarequeaziz on Mon, 14 April 2008 13:13
		Re: Interpolation By: Spon on Mon, 14 April 2008 11:44
		Re: Interpolation By: Spon on Mon, 14 April 2008 08:34
		Re: Interpolation By: tarequeaziz on Sat, 12 April 2008 17:56
		Re: Interpolation By: ben.bighair on Sat, 12 April 2008 15:26
		Re: Interpolation By: tarequeaziz on Sat, 12 April 2008 13:24
		Re: Interpolation By: ben.bighair on Sat, 12 April 2008 08:57
		Re: interpolation By: Yngvar Larsen on Thu, 08 December 2011 13:24
		Re: interpolation By: Brian Wolven on Thu, 08 December 2011 12:57
		Re: interpolation By: anil on Thu, 08 December 2011 04:15
		Re: interpolation By: anil on Thu, 08 December 2011 04:15
		Re: interpolation By: anil on Thu, 08 December 2011 04:15
		Re: interpolation By: Kenneth P. Bowman on Wed, 07 December 2011 14:25
		Re: interpolation By: Brian Wolven on Wed, 07 December 2011 12:27
		Re: interpolation By: David Fanning on Wed, 07 December 2011 12:13
		Re: interpolation By: Jeremy Bailin on Wed, 07 December 2011 12:07
		Re: interpolation By: anil on Wed, 07 December 2011 09:50
		Re: interpolation By: Russell[1] on Wed, 07 December 2011 08:42
		Re: interpolation By: anil on Wed, 07 December 2011 05:51
		Re: interpolation By: anil on Wed, 07 December 2011 05:48

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