Statistics Toolbox | ![]() ![]() |
Syntax
Description
Y = polyval(p,X)
returns the predicted value of a polynomial given its coefficients, p
, at the values in X
.
[Y,DELTA] = polyval(p,X,S)
uses the optional output S
generated by polyfit
to generate error estimates, Y
± DELTA. If the errors in the data input to polyfit
are independent normal with constant variance, Y
± DELTA contains at least 50% of the predictions.
If p
is a vector whose elements are the coefficients of a polynomial in descending powers, then polyval(p,X)
is the value of the polynomial evaluated at X
. If X
is a matrix or vector, the polynomial is evaluated at each of the elements.
The polyval
function is part of the standard MATLAB language
.
Examples
Simulate the function y = x, adding normal random errors with a standard deviation of 0.1. Then use polyfit
to estimate the polynomial coefficients. Note that predicted Y
values are within DELTA of the integer X
in every case.
[p,S] = polyfit(1:10,(1:10) + normrnd(0,0.1,1,10),1); X = magic(3); [Y,D] = polyval(p,X,S) Y = 8.0696 1.0486 6.0636 3.0546 5.0606 7.0666 4.0576 9.0726 2.0516 D = 0.0889 0.0951 0.0861 0.0889 0.0861 0.0870 0.0870 0.0916 0.0916
See Also
polyfit
, polytool
, polyconf
![]() | polytool | prctile | ![]() |