Plot a vector with a given angle against the y-axis

Hi, so as the title states I want to simply plot a line that will make an angle I already know with the y axis, as this line will be plotted in the same figure as other graphs I want it to also be scaled such that it can be seen in these figures as the order of magnitude changes. I know that the vector will have the slope k = sin(angle)/cos(angle) (as it will always intercept the origin) but how do I plot it so that its range is covered by the whole figure. I have attached a figure that shows an example of what I'm trying to plot

Answer 1

[Paul]

Something like this? Note that the line won't won't resize if the axes are resized. If you want something like that, you might be able to use a combination of xline and hgtransform, but I didn't try it.

rng(100);
figure;scatter(randn(100,1),randn(100,1))
theta = 30;
yl = ylim;
line([yl(1)*tand(30) yl(2)*tand(30)],[yl(1) yl(2)])

Answer 2

[Star Strider]

Another approach —

thetad = 280;                                                           % Desired Angle (Guessing Value)
x = randn(100,1)*2;
y = randn(100,1);
% thetad = 360*rand

arcang = linspace(mod(thetad, 180),  90,  25);
arc = @(yv) [(max(yv)/2)*cosd(arcang); (max(yv)/2)*sind(arcang)];

figure
scatter(x, y, 'x')
hold on
plot(xlim*cosd(thetad), xlim*sind(thetad), '-b', 'LineWidth',2)
arcs = arc(ylim);
plot(arcs(1,:), arcs(2,:), '-b', 'LineWidth',2)
hold off
axis('equal')
title('Normal Ticks, Tick Labels, & Axes, With Solid Lines For Axes')
Ax = gca;
Ax.XAxisLocation = 'origin';
Ax.YAxisLocation = 'origin';
text(median(arcs(1,:)), median(arcs(2,:)), '\theta', 'Horiz','center', 'Vert','bottom', 'Color','b', 'FontSize',16)%, 'FontWeight','bold')

% get(Ax)


figure
scatter(x, y, 'x')
hold on
plot(xlim*cosd(thetad), xlim*sind(thetad), '-b', 'LineWidth',2)
arcs = arc(ylim);
plot(arcs(1,:), arcs(2,:), '-b', 'LineWidth',2)
hold off
axis('equal')
xline(0, '--k', 'LineWidth',2)                                          % Draw Y-Axis
yline(0, '--k', 'LineWidth',2)                                          % Draw X-Axis
title('Invisible Itcks, Tick Labels, & Axes, With Dashed Lines For Axes')
Ax = gca;
Ax.XAxis.Visible = 0;
Ax.YAxis.Visible = 0;
text(median(arcs(1,:)), median(arcs(2,:)), '\theta', 'Horiz','center', 'Vert','bottom', 'Color','b', 'FontSize',16)%, 'FontWeight','bold')

EDIT — (20 Apr 2024 at 19:14)

Made ‘arcang’ more robust.

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