Problem performing calculation with meshgrid variables

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Joe
Joe 2015-9-23
评论： Joe 2015-9-23
Hi,
I'm a matlab novice - hoping someone can point me in the right direction here!
I'm trying to write a short code to transform pixels from an image captured on a flat x-ray area detector (486x193 pixels, pix width 175microns) at an arbitrary orientation to a sample into a useful system relative to the sample being measured. I want to produce a contour plot of the result.
I'm using meshgrid to create variables X and Y for the x and y positions of pixels on the detector, and performing a calculation given in Hammersley 1995 to give me an equivalent diffraction angle Q2 at any pixel on the detector, using the following code:
%set up Xdim and Ydim parameters, relative to centre pixel x0,y0
x = linspace(1,486,486)
y = linspace(1, 193,193)
w_pix = 175e-3
[X,Y]=meshgrid(x,y)
x0 = 242
y0=108
Xdim = (X - x0)*w_pix
Ydim = (Y-y0)*w_pix
zref = 502
%perform transformation - case 1, detector perpendicular to beam
Q2 = atan(power((power(Xdim,2) + power(Ydim,2))/power(zref,2),0.5))
%perform transformation - case 2, detector rotated 35 deg to detector normal
qtilt_rad = pi*35/180
Q2_tilt = atan(power((power(Xdim*cos(qtilt_rad),2)+power(Ydim,2))/(power(zref+sin(qtilt_rad)*Xdim,2)),0.5))
Of the above 2 cases, the first variable Q2 comes out sized [193,486] as I need it, but for Q2_tilt it is [193,193], which can't be contoured against X and Y. I have no idea why the latter should happen - can anyone help?
Many Thanks,
Joe

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采纳的回答

Walter Roberson
Walter Roberson 2015-9-23
Q2_tilt = atan( power( (power( Xdim*cos(qtilt_rad),2) + power(Ydim,2)) ./ (power(zref+sin(qtilt_rad)*Xdim,2)), 0.5));
Difference: / became ./

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