How to make a line given a point through which it is passing through and angle from x-axis.

I want to make a line passing through a point and having slope. And want to check which data points lie on the line. Like given in the figure I want to draw AB line.

Answer 1

[Ameer Hamza]

Try this

x = 103.3;
y = 31.1;

angle_yAxis = 139;
angle_xAxis = 90 + (180-139);
slope = tand(angle_xAxis);

x_range = 102:0.01:106;
y_range = slope*(x_range - x) + y;

figure;
plot(x, y, '+', 'LineWidth', 2, 'MarkerSize', 8);
hold on
plot(x_range, y_range);
xlim([102 106]);
ylim([30 33]);

vectors x_range and y_range contain the points lying on the line.

[TAPAS]

Thank you.

Now suppose if i try to find the distance between the point(x,y) and (x_range,y_range),as we know the distance will always be a positive number but what I want to do is after finding the distance make all distance left to the point(x,y) negative sign before it and distance right to the point(x,y) with positive sign.

can you do this??

[Ameer Hamza]

How are you calculating the distance? Can you show the code for that?

[TAPAS]

x = 103.3;
y = 31.1;

angle_yAxis = 139;
angle_xAxis = 90 + (180-139);
slope = tand(angle_xAxis);
x_range = 102:0.001:106;
y_range = slope*(x_range - x) + y;
W=30<=y_range&y_range<=33;
y_range1=y_range(W);
x_range1=x_range(W);
dist_deg=distance(x,y,x_range1,y_range1);
dist_km=deg2km(dist_deg);
figure;
plot(x, y, '+', 'LineWidth', 2, 'MarkerSize', 8);
hold on
plot(x_range, y_range);
xlim([102 106]);
ylim([30 33]);
hold on
plot(xv,yv);

Here the 'dist_km',you can see first it has higher value then decreasing again increasing after a certain value.I want to make the initial value -ve with the same magnitude and then +ve after that certain value from which it is again start increasing.It will be easy for me for a plot first -ve then crosses zero then +ve.

[Ameer Hamza]

try this

x = 103.3;
y = 31.1;
angle_yAxis = 139;
angle_xAxis = 90 + (180-139);
slope = tand(angle_xAxis);
x_range = 102:0.001:106;
y_range = slope*(x_range - x) + y;

dist = pdist2([x y], [x_range.' y_range.']);
mask = x_range < x;
dist(mask) = dist(mask)*-1;

figure;
plot(x, y, '+', 'LineWidth', 2, 'MarkerSize', 8);
hold on
plot(x_range, y_range);
xlim([102 106]);
ylim([30 33]);

figure;
plot(x_range, dist);

[TAPAS]

Actually my data points are lat(y,y_range),long(x,x_range).so i think distance command will be a good choice.

[Ameer Hamza]

You can change the line to

dist = distance(x, y, x_range.', y_range.');