# How to plot a line with specific line slope ?

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Sierra on 21 May 2022
Answered: Sam Chak on 21 May 2022
i have a one coordinates (x1,y1).
(actually i have a lot of coordinates.)
what i want to know is how to plot a line with specific line slope and (x1,y1).
thanks!

Voss on 21 May 2022
You have to decide where the plotted line segment should start and end.
Here's one way you might do that, which is to plot the line between two points whose x-coordinates are a certain amount away from x1:
x1 = 3;
y1 = 4;
% slope = 2:
m = 2;
% plot the point (x1,y1):
plot(x1,y1,'ko','MarkerFaceColor','k');
hold on
% plot a line segment with x going from x1-1 to x1+1.
% note that if x changes by 1, then y changes by m
% (that's the definition of the slope of a line):
plot(x1+[-1 1],y1+m*([-1 1]),'b','LineWidth',2)
% another line segment going from x1-4 to x1+2,
% with the same slope:
plot(x1+[-4 2],y1+m*([-4 2]),'--r')
axis equal

Sam Chak on 21 May 2022
But you can only determine the slope if you know the coordinates of the adjacent points.
Are you trying to plot the vector of a particular point when its coordinate is given?