## functions in cheby.i - c

cheby_deriv
```
cheby_deriv(fit)

returns Chebyshev fit to the derivative of the function of the
input Chebyshev FIT.

Interpreted function, defined at i/cheby.i   line 76

```

cheby_eval
```
cheby_eval(fit, x)

evaluates the Chebyshev fit (from cheby_fit) at points X.
the return values have the same dimensions as X.

Interpreted function, defined at i/cheby.i   line 36

```

cheby_fit
```
fit = cheby_fit(f, interval, n)
or fit = cheby_fit(f, x, n)

returns the Chebyshev fit (for use in cheby_eval) of degree N
to the function F on the INTERVAL (a 2 element array [a,b]).
In the second form, F and X are arrays; the function to be
fit is the piecewise linear function of xp interp(f,x,xp), and
the interval of the fit is [min(x),max(x)].

The return value is the array [a,b, c0,c1,c2,...cN] where [a,b]
is the interval over which the fit applies, and the ci are the
Chebyshev coefficients.  It may be useful to use a relatively
large value of N in the call to cheby_fit, then to truncate the
resulting fit to fit(1:3+m) before calling cheby_eval.

Interpreted function, defined at i/cheby.i   line 7

```

cheby_integ
```
cheby_integ(fit)
or cheby_integ(fit, x0)

returns Chebyshev fit to the integral of the function of the
input Chebyshev FIT.  If X0 is given, the returned integral will
be zero at X0 (which should be inside the fit interval fit(1:2)),
otherwise the integral will be zero at x=fit(1).

Interpreted function, defined at i/cheby.i   line 54

```