Postprocessing Splines
You can use the following commands with any example spline, such as thecs
,ch
andsp
examples constructed in the sectionCubic Spline Interpolation.
首先构造一个花键,例如:
sp = spmak(1:6,0:2)
To display a plot of the spline:
fnplt(sp)
To get the value ata
, use the syntaxfnval(f,a)
, for example:
fnval(sp,4)
To construct the spline's second derivative:
DDf = fnder(fnder(sp))
An alternative way to construct the second derivative:
DDf = fnder(sp,2);
To obtain the spline's definiteintegral over an interval [a
..b
], in this example from 2 to 5:
diff(fnval(fnint(sp),[2;5]))
To compute the difference between two splines, use the formfncmb(sp1,'-',sp2)
, for example:
fncmb(sp,'-',DDf);