sftool help
in [Matlab]
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From: Andreas on 13 Oct 2009 12:25 Hi, I have a simple question regarding sftool. I try to get started with a simple test example such that: x=-2:.2:2; y= -2:.2:2; [X,Y] = meshgrid(x, y); Z = X .* exp(-X.^2 - Y.^2); surf(X,Y,Z); sftool(x,y,Z); However, this gives an error saying "Invalid inputs to SFTOOL, input vectors must be double. Z-data is invalid." I am not sure if I understand the logic of this program right but it does not make sense to me that Z (the surface to be fitted) should be a vector and not a matrix... Can anyone help me out on this. Andreas
From: Steven Lord on 13 Oct 2009 13:14 "Andreas " <andreasm(a)atmos.washington.edu> wrote in message news:hb29lh$etb$1(a)fred.mathworks.com... > Hi, > > I have a simple question regarding sftool. > I try to get started with a simple test example such that: > > x=-2:.2:2; > y= -2:.2:2; > [X,Y] = meshgrid(x, y); > Z = X .* exp(-X.^2 - Y.^2); > surf(X,Y,Z); > sftool(x,y,Z); > > However, this gives an error saying "Invalid inputs to SFTOOL, input > vectors must be double. Z-data is invalid." > > I am not sure if I understand the logic of this program right but it does > not make sense to me that Z (the surface to be fitted) should be a vector > and not a matrix... Why not? That's what the documentation indicates SFTOOL expects. http://www.mathworks.com/access/helpdesk/help/toolbox/curvefit/sftool.html "sftool(x,y,z) creates a fit to x and y inputs (or predictor data) and z output (or response data). x, y, and z must be double vectors of the same length, with two or more elements. sftool opens Surface Fitting Tool if necessary." Use the following command instead of your last one above: sftool(X(:), Y(:), Z(:)) This makes all three inputs double vectors of the same length, which is what SFTOOL expects. -- Steve Lord slord(a)mathworks.com comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
From: Andreas on 13 Oct 2009 15:28 "Steven Lord" <slord(a)mathworks.com> wrote in message <hb2cgg$lav$1(a)fred.mathworks.com>... > > "Andreas " <andreasm(a)atmos.washington.edu> wrote in message > news:hb29lh$etb$1(a)fred.mathworks.com... > > Hi, > > > > I have a simple question regarding sftool. > > I try to get started with a simple test example such that: > > > > x=-2:.2:2; > > y= -2:.2:2; > > [X,Y] = meshgrid(x, y); > > Z = X .* exp(-X.^2 - Y.^2); > > surf(X,Y,Z); > > sftool(x,y,Z); > > > > However, this gives an error saying "Invalid inputs to SFTOOL, input > > vectors must be double. Z-data is invalid." > > > > I am not sure if I understand the logic of this program right but it does > > not make sense to me that Z (the surface to be fitted) should be a vector > > and not a matrix... > > Why not? That's what the documentation indicates SFTOOL expects. > > http://www.mathworks.com/access/helpdesk/help/toolbox/curvefit/sftool.html > > "sftool(x,y,z) creates a fit to x and y inputs (or predictor data) and z > output (or response data). x, y, and z must be double vectors of the same > length, with two or more elements. sftool opens Surface Fitting Tool if > necessary." > > Use the following command instead of your last one above: > > sftool(X(:), Y(:), Z(:)) > > This makes all three inputs double vectors of the same length, which is what > SFTOOL expects. > > -- O.k., I figured it out. Thanks. I have another more advanced question: I want to exclude some of my data from the fitting procedure. There exist a simple way of doing this in the cftool but I could not find this option in the sftool and the documentation doen't say about this as far as I can see. So, how would that work? > Steve Lord > slord(a)mathworks.com > comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ >
From: Steven Lord on 14 Oct 2009 10:01 "Andreas " <andreasm(a)atmos.washington.edu> wrote in message news:hb2kck$g79$1(a)fred.mathworks.com... *snip* > O.k., I figured it out. Thanks. > I have another more advanced question: > I want to exclude some of my data from the fitting procedure. There exist > a simple way of doing this in the cftool but I could not find this option > in the sftool and the documentation doen't say about this as far as I can > see. So, how would that work? You could use the Exclude Outliers tool: http://www.mathworks.com/access/helpdesk/help/toolbox/curvefit/brviv3f-1.html#brybu6k-1 or filter out the points you want to exclude from your vectors and import the shortened vectors into SFTOOL, or perhaps just set the weights for those excluded points to 0. -- Steve Lord slord(a)mathworks.com comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
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