Drawing Lines on a Graph

I have two intersecting graphs plotted on the same axis,

ie: plot(V,P1,V,P2)

where P1 and P2 are variations of the same function

I would like to have a line drawn vertically to the x axis, and horizonally to the y axis from the point where these two lines intersect

How would I complete such a command?

Thanks

Answer 1

[Mark Sherstan]

Find the intersection points with the polyxpoly function and then use the line function to draw your desired line. If you need further help please post your data.

Answer 2

[Star Strider]

If you do not have the Mapping Toolbox, this will likely work:

V = linspace(0, 30);                                        % Arbitrary Vector
Pfcn = @(a,t) a(1).*exp(t/10) + a(2);                       % Arbitrary Function

P1 = Pfcn([ 4.2, -42],V);                                   % Evaluate Function
P2 = Pfcn([-4.2, 4.2],V);                                   % Evaluate Function

xint = interp1((P1-P2), V, 0);                              % Find ‘x’ At Intersection
yint = interp1(V,P1, xint);                                 % Find ‘y’ At Intersection

figure
plot(V,P1,V,P2)                                             % Plot Functions
hold on
xl = xlim;
yl = ylim;
plot(xint*[1 1], yl, 'g',  xl, yint*[1 1],'g')              % Plot Lines
hold off