Documentation

fsurfht

Interactive contour plot

Syntax

fsurfht(fun,xlims,ylims)
fsurfht(fun,xlims,ylims,p1,p2,p3,p4,p5)

Description

fsurfht(fun,xlims,ylims) is an interactive contour plot of the function specified by the text variable fun. The x-axis limits are specified by xlims in the form [xmin xmax], and the y-axis limits are specified by ylims in the form [ymin ymax].

fsurfht(fun,xlims,ylims,p1,p2,p3,p4,p5) allows for five optional parameters that you can supply to the function fun.

The intersection of the vertical and horizontal reference lines on the plot defines the current x value and y value. You can drag these reference lines and watch the calculated z-values (at the top of the plot) update simultaneously. Alternatively, you can type the x value and y value into editable text fields on the x-axis and y-axis.

Examples

Plot the Gaussian likelihood function for the gas.mat data.

Create a function containing the following commands, and name it gauslike.m.

function z = gauslike(mu,sigma,p1)
n = length(p1);
z = ones(size(mu));
for i = 1:n
z = z .* (normpdf(p1(i),mu,sigma));
end

The gauslike function calls normpdf, treating the data sample as fixed and the parameters µ and σ as variables. Assume that the gas prices are normally distributed, and plot the likelihood surface of the sample.

fsurfht('gauslike',[112 118],[3 5],price1) The sample mean is the x value at the maximum, but the sample standard deviation is not the y value at the maximum.

mumax = mean(price1)
mumax =
115.1500
sigmamax = std(price1)*sqrt(19/20)
sigmamax =
3.7719