Minimum of function in given interval
[minval,minsite] = fnmin(f,...)
Example 1. We construct and plot a spline f with many local extrema, then compute its maximum as the negative of the minimum of –f. We indicate this maximum value by adding a horizontal line to the plot at the height of the computed maximum.
rng(21); f = spmak(1:21,rand(1,15)-.5); fnplt(f) maxval = -fnmin(fncmb(f,-1)); hold on, plot(fnbrk(f,'interv'),maxval([1 1])), hold off
[y,x] = fnmin(spmak(1:5,-1))
to return -2/3 for y and 3 for x.
fnmin first changes the basic interval of the function to the given interval, if any. On the interval, fnmin then finds all local extrema of the function as left and right limits at a jump and as zeros of the function's first derivative. It then evaluates the function at these extrema and at the endpoints of the interval, and determines the minimum over all these values.