How can I plot a smooth ROC curve with non-monotonically ascending points?

I'm trying to plot a ROC curve, but the curve has to be smooth. So I'm using the interpolation to make it. However, when I use the 'pchip' function, the line ignores one of these points. I guess it happens due the vector created when I use the linspace function because the coordinates are not all monotonically ascending. Code:

FPRate = [1.0000    0.5349    0.2405    0.1653    0.2199];
TPRate = [0.8288    1.0000    0.9254    0.6190    0.0412];

    F = linspace(FPRate(1,1),FPRate(1,5),10000);
    T = interp1(FPRate,TPRate,F,'pchip');

    plot(F,T,'k');

    hold on
    plot(FPRate,TPRate,'.','MarkerSize',20);

If I change the code and use max and min values rather than the vector address:

F = linspace(min(FPRate),max(FPRate),10000);
T = interp1(FPRate,TPRate,F,'pchip');
plot(F,T,'k');
hold on
plot(FPRate,TPRate,'.','MarkerSize',20);

The problem here is that the plot doesn't follow the vector address but the values it contains. Is there any way to plot a graph like this one below but in a smooth form?

plot(FPRate,TPRate,'k');
hold on
plot(FPRate,TPRate,'.','MarkerSize',20);