plot x, y and direction

Hi all,

I have values for x, y, and Azimuth, where Azimuth is in range of 0 to 360 degree measured from the North in clockwise.

how can I plot them in a 2D graph which shows the point with direction arrow?

 x                                              
607261.185639785    
607280.329476425    
607367.827131141    
 y
4821687.60219055
4821678.02095485
4821646.17145724
 direction
108
108
115.142857142857

Answer 1

[Walter Roberson]

You probably want to use quiver() to plot your vector fields.

Answer 2

[zheng]

Here is sample I found to deal with my problem

but only question is how to set the angle are measured from North in clockwise (Azimuth)

clear; clc; close all

% Arrows in the following
% red = 0 to 90 degrees (counterclockwise)
% green = 91 to 180 degrees
% blue = 181 to 270 degrees
% cyan = 271 to 360 degrees
% Data is organize as (x, y, theta in degrees)
data = [607261.185639785  4821687.60219055  108
607280.329476425  4821678.02095485  108
607367.827131141  4821646.17145724  115.142857142857
607423.238973159  4821613.59562066  120
];

% Plot to figure 1
figure(1);

% Identify data from 1st quadrant and store in q1, identify data from 2nd quadrant
% goes to q2, and so on. A value of 1 indicates it is in the quadrant, 0 otherwise
q1 = (data(:,3) <= 90);
q2 = (data(:,3) > 90) .* (data(:,3) <= 180);
q3 = (data(:,3) > 180) .* (data(:,3) <= 270);
q4 = (data(:,3) > 271) .* (data(:,3) <= 360);

hold on; 
% See DOC QUIVER
% Use QUIVER to specify the start point (tail of the arrow) and direction based on angle
% q1, q2, q3, and q4 are used to generate four different QUIVER handles (h1, h2, h3, and h4)
% This is necessary for varying colors based on direction
% Based on equations: x = x0 + r*cos(theta), y = y0 + r*sin(theta)
% In the usage below, x0 = data(:,1), y0 = data(:,2), theta = data(:,3) * pi / 180
% Can also specify a scale factor as the last argument to quiver (not specified below)

h1 = quiver(data(q1 == 1,1), data(q1 == 1,2), cos(data(q1 == 1,3) * pi/180), sin(data(q1 == 1,3) * pi/180));
h2 = quiver(data(q2 == 1,1), data(q2 == 1,2), cos(data(q2 == 1,3) * pi/180), sin(data(q2 == 1,3) * pi/180)); % sin is negative in 2nd quadrant
h3 = quiver(data(q3 == 1,1), data(q3 == 1,2), cos(data(q3 == 1,3) * pi/180), sin(data(q3 == 1,3) * pi/180));
h4 = quiver(data(q4 == 1,1), data(q4 == 1,2), cos(data(q4 == 1,3) * pi/180), sin(data(q4 == 1,3) * pi/180)); % cos is negative in 4th quadrant

% Set colors to red for 1st quadrant, blue for 2nd, green for 3rd, cyan for 4th
% Also, turn scaling off. get(h1) will return additional property-value pairs
set(h1, 'Color', [1 0 0], 'AutoScale', 'off')
set(h2, 'Color', [0 1 0], 'AutoScale', 'off')
set(h3, 'Color', [0 0 1], 'AutoScale', 'off')
set(h4, 'Color', [0 1 1], 'AutoScale', 'off')
% Done plotting
hold off;

Answer 3

[Walter Roberson]

To change from compass direction (in degrees) with north being 0, to standard cartesian angles measured counter-clockwise from y=0, use

planar_angle = mod(90 - compass_angle, 360);

Answer 4

[zheng]

for i=1:length(data(:,1))
if data(i,3)<=90
    data(:,4)=90-data(i,3);
end
if data(i,3)>90 && data(i,3)<=180
        data(i,4)=360-(data(i,3)-90);
end
if data(i,3)>180 && data(i,3)<=270
            data(i,4)=180+(270-data(i,3));
end
if data(i,3)>270 && data(i,3)<=360
                data(i,4)=90+(360-data(i,3));
end
end
q1 = (data(:,4) <= 90);
q2 = (data(:,4) > 90) .* (data(:,4) <= 180);
q3 = (data(:,4) > 180) .* (data(:,4) <= 270);
q4 = (data(:,4) > 271) .* (data(:,4) <= 360);

hold on; 

h1 = quiver(data(q1 == 1,1), data(q1 == 1,2), cos(data(q1 == 1,3) * pi/180), sin(data(q1 == 1,3) * pi/180));
h2 = quiver(data(q2 == 1,1), data(q2 == 1,2), cos(data(q2 == 1,3) * pi/180), sin(data(q2 == 1,3) * pi/180)); % sin is negative in 2nd quadrant
h3 = quiver(data(q3 == 1,1), data(q3 == 1,2), cos(data(q3 == 1,3) * pi/180), sin(data(q3 == 1,3) * pi/180));
h4 = quiver(data(q4 == 1,1), data(q4 == 1,2), cos(data(q4 == 1,3) * pi/180), sin(data(q4 == 1,3) * pi/180)); % cos is negative in 4th quadrant

could you please explain what does data(q3 == 1,1) mean?

I used if end to convert my azimuth angel to the angle measurend from x = 0 ( as used in this sample code). But it doesnt work. the sample code conside my azimuth angle as the angle measured in contourclockwised from x =0; tks alot

Answer 5

[Walter Roberson]

The q variables are logical vectors indicating whether each angle is in a particular quadrant. data(q3==1,1) selects only the rows of data that are in quadrant 3, and selects column 1 from the resulting array.

Instead of modifying the existing code to change the logic, go back to the original logic, but copy the assignment of those constants to data into a new variable planar_data, then comment out the assignment to data; then in the planar_data array, set the third column to your sample compass degrees that you want for testing purposes. After that step, assign

data = [planar_data(:,1,2) mod(90 -planar_data(:,3),360)];

Once you have the demonstration going, make it in to a function that takes planar_data as a parameter instead of assigning hard-coded values to it.

Answer 6

[Ankita Misra]

I have Landsat solar angles which i would like to plot as arrows . I have three variables x,y and the angle . How do I plot them to show meaningful directions ?

[Walter Roberson]

I would suggest using quiver(). You could use sin(angle) and cos(angle) as the u and v (or is it the other way around?)

Answer 7

[theodore panagos]

The formula f(E,N) give an angle that starts from the north,is clockwise,runs from 0 to 360 degrees

and is used in surveying.

f(E,N)=180/pi()*(pi()-pi()/2*(1+sign(N))*(1-sign(E^2))-pi()/4*(2+sign(N))*sign(E) -sign(N*E)*atan((abs(N)-abs(E))/(abs(N)+abs(E))))

There is N(northing)=N2-N1 and E(easting)=E2-E1 ,the formula works for any value of N and E and the result for N=E=0 is undefined.