'poly1' unrecognized

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Igor
Igor 2023-5-11
评论： Walter Roberson 2023-5-12
Dear all
I am trying to to a fit to simple polynomial function.
However, when I try to use 'poly1' as a fittype it gives: Unrecognized function or variable 'poly1'.
I am using the command form as in the library f = fit(x, y, 'poly1'), or f = fit(x, y, poly1) -nothing works
how is it possible? I though it should be in the library as written here:
https://uk.mathworks.com/help/curvefit/list-of-library-models-for-curve-and-surface-fitting.html#btbcvnl
thank you

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回答（1 个）

Chunru
Chunru 2023-5-11
Ran in:
x = (0:0.2:5)';
y = 2*exp(-.2*x) + 0.5 * randn(size(x));
f = fit(x, y, 'poly1');
% check the path of fit
which fit
/MATLAB/toolbox/curvefit/curvefit/fit.m
plot(f, x, y)
% f = fit(x, y, poly1) % not working unless poly1='poly1';
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Igor
Igor 2023-5-12
Hi
thank you for answer, yes I actually names the script file as fit.m so that could cause problems.
I think I have curve fitting toolbow add.
What is the function of - which fit?
Walter Roberson
Walter Roberson 2023-5-12
@Igor
which fit
asks MATLAB to first search the workspace (and calling parameters, and any shared variables) to see whether the name fit is associated with a variable in scope, and if so then tells you that it is a variable. If fit is not found as a variable in scope, then MATLAB searches for functions named fit, and if one is found then MATLAB will tell you the path to the function that was found.
Note that the search will not necessarily find the same fit that a call to fit will resolve to. If the parameters to fit involve a class that defines a method named fit then which fit will not find that method. You can, however, ask for (for example)
which fit(x)
in which case MATLAB will search for the fit that would be called if a value with the same type as x were to be passed to fit

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