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Asked by hanciong on 25 Jan 2013

Hello all, I have a problem. I have the following scipt to make 2D interpolation of some function fu(x,y) = x^2y-y^2x. There is no problem if both x and y are scalars. However, if I call fuint with x scalar and y row vector for example, the output is column vector. also, if I call fuint with x column vector and y scalar, the output is row vector. see the two lines in which I write comment %-->problem here. The problem is that, quadgk can't integrate @(y) fuint(3,y), because input size is not the same as output. how should I modify this such that the size of the output is the same as input, if either x or y is scalar? Thanx ==========================================

clear all

xcoba = linspace(-5,5,50); ycoba = linspace(-5,5,50);

fu = @(x,y) x.^2.*y - y.^2.*x;

[xgrid,ygrid] = ndgrid(xcoba,ycoba);

fugrid = fu(xgrid,ygrid);

fuint = @(x,y) interp2(xgrid',ygrid',fugrid',x,y,'cubic',NaN);

fuint(1,[2,3,4]) %--> problem here

fuint([2;3;4],1) %--> problem here

quadgk(@(y) fuint(3,y), -3,3)

=======================================

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Answer by John Petersen on 25 Jan 2013

you can make the scalar into an array with

X = x*ones(1,length(y));

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