Plotting just x = 1 over an x and y graph

Howdy howdy howdy,

I have this following code which gives me two out of the three lines I need:

a = 2;
x = linspace(1,100,10);
for i=1:length(x)
    y1(i) = 0*(i);
    y2(i) = ((a-i).*(1+i))/i;
end
figure
plot(x,y1,x,y2)

I need to plot an additional line on the same plot. That line needs to be x = 1/(a-1) = 1.

Can someone help me?

Cheers! E

Answer 1

[Walter Roberson]

yl = get(gca, 'YLim');
line( [1 1], yl )

This would draw a vertical line the height of the axes. (Note: if you later make the axes taller, the line will not automatically adjust itself.)

[Erin W]

Beautiful, thank you so much!

Answer 2

[Guillaume]

a = 2;
x = 1:linspace(1, 100, 10);
y = 1:numel(x);

plot(x, [zeros(size(x)); (a-y).*(1+y)./y; repmat(1/(a-1), 1, numel(x))]);

is probably the simplest. The loop is certainly not required.

I don't particularly see the point of the brackets in 0*(i), and even less the point of the multiplication, since y1(i) = 0 would convey exactly the same with better readability.

In your y2 expression, a and i are both scalar, so .* is the same as * and ./ is the same as /, but really you should be consistent.

[Erin W]

It's odd because I was getting an error until I put that period in. But MATLAB goofs a lot for me.

I just was playing around with things. I'm not a great coder by any means. But thank you. You have been extremely helpful.