I want to plot current data (direction and magnitude) as vectors in a single plot

Hi! I'm trying to plot a timeseries of current data in away that I have seen wind velocity data displayed like in the example attached. I have current direction (dir_adp3_mx) and magnitude (mag_adp3_mx) and my timestamps (MX). Can I use this data to make a plot of current velocity like the plot of wind speeds below? I think I need to use the quiver or feather functions but I am confused on how to make the X axis time in either case. Please help if you have ideas. I attached the data I am working with as data.mat.

Answer 1

[Mathieu NOE]

hello Heidi

below some code with quiver vs feather display. depneds of your preferences - seem I got better angular rendering with quiver.

also note that I have dispayed only the first 100 samples to get a better picture to show the differences in rendering

I have manually added a baseline to the standard quiver display - so at the end it's very similar to what feather do;

you can of course remove that

hope it helps

Mathieu

load data.mat

% data file content : 
%   Name                Size            Bytes  Class     Attributes
% 
%   MX               4888x1             39104  double              
%   dir_adp3_mx      4888x1             39104  double              
%   mag_adp3_mx      4888x1             39104  double 

%     quiver(X,Y,U,V) plots velocity vectors as arrows with components (u,v)
%     at the points (x,y).  The matrices X,Y,U,V must all be the same size
%     and contain corresponding position and velocity components (X and Y
%     can also be vectors to specify a uniform grid).  quiver automatically
%     scales the arrows to fit within the grid.

% we need to create the X and Y coordinates of each vector
% NB : current direction (dir_adp3_mx) is in degrees

direction_rad = pi/180*dir_adp3_mx;
Xvec= mag_adp3_mx.*cos(direction_rad);
Yvec= mag_adp3_mx.*sin(direction_rad);

% create x,y points for quiver %     quiver(X,Y,U,V) plots velocity vectors
% as arrows with components (u,v) at the points (x,y).
time = MX-MX(1); % so x start at 0 (needed ?)
y = zeros(size(x));  % base line 

samples = 100;  % to remove if necessary
% 
figure(1)
quiver(time(1:samples),y(1:samples),Xvec(1:samples),Yvec(1:samples),'.');
% add central line
hold on
plot(time(1:samples),y(1:samples));
hold off

%     quiver(...,LINESPEC) uses the plot linestyle specified for
%     the velocity vectors.  Any marker in LINESPEC is drawn at the base
%     instead of an arrow on the tip.  Use a marker of '.' to specify
%     no marker at all.  See PLOT for other possibilities.

figure(2)
feather(Xvec(1:samples),Yvec(1:samples))