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6721
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1 function interpimages (nm, typ) |
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2 bury_output (); |
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3 if (strcmp (nm, "interpft")) |
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4 t = 0 : 0.3 : pi; dt = t(2)-t(1); |
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5 n = length (t); k = 100; |
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6 ti = t(1) + [0 : k-1]*dt*n/k; |
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7 y = sin (4*t + 0.3) .* cos (3*t - 0.1); |
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8 yp = sin (4*ti + 0.3) .* cos (3*ti - 0.1); |
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9 plot (ti, yp, 'g', ti, interp1(t, y, ti, 'spline'), 'b', ... |
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10 ti, interpft (y, k), 'c', t, y, 'r+'); |
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11 legend ('sin(4t+0.3)cos(3t-0.1','spline','interpft','data'); |
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12 print (strcat (nm, ".", typ), strcat ("-d", typ)) |
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13 elseif (strcmp (nm, "interpn")) |
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14 x = y = z = -1:1; |
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15 f = @(x,y,z) x.^2 - y - z.^2; |
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16 [xx, yy, zz] = meshgrid (x, y, z); |
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17 v = f (xx,yy,zz); |
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18 xi = yi = zi = -1:0.1:1; |
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19 [xxi, yyi, zzi] = ndgrid (xi, yi, zi); |
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20 vi = interpn(x, y, z, v, xxi, yyi, zzi, 'spline'); |
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6723
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21 mesh (zi, yi, squeeze (vi(1,:,:))); |
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6721
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22 print (strcat (nm, ".", typ), strcat ("-d", typ)) |
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23 elseif (strcmp (nm, "interpderiv")) |
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24 t = 0 : 0.3 : pi; dt = t(2)-t(1); |
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25 n = length (t); k = 100; dti = dt*n/k; |
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26 ti = t(1) + [0 : k-1]*dti; |
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27 y = sin (4*t + 0.3) .* cos (3*t - 0.1); |
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28 ddyc = diff(diff(interp1(t,y,ti,'cubic'))./dti)./dti; |
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29 ddys = diff(diff(interp1(t,y,ti,'spline'))./dti)./dti; |
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30 ddyp = diff(diff(interp1(t,y,ti,'pchip'))./dti)./dti; |
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31 plot (ti(2:end-1), ddyc,'g+',ti(2:end-1),ddys,'b*', ... |
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32 ti(2:end-1),ddyp,'c^'); |
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33 legend('cubic','spline','pchip'); |
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34 print (strcat (nm, ".", typ), strcat ("-d", typ)) |
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35 endif |
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36 bury_output (); |
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37 endfunction |
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38 |
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39 ## Use this function before plotting commands and after every call to |
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40 ## print since print() resets output to stdout (unfortunately, gnpulot |
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41 ## can't pop output as it can the terminal type). |
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42 function bury_output () |
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43 f = figure (1); |
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44 set (f, "visible", "off"); |
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45 endfunction |
