4D Array plot data between two gps points

Hi!

I have a 4D array

u1=rand(241,97,1,1637), that is (lon,lat,depth,time)

If I select a lon, lets say lon = 50 then I plot ud = squeeze(u1(50,:,:,:)), that makes an extraction of data at 50 of lon,

but what I want is to make this plot between lon = 10 and lon = 70, like a diagonal and not a line folowing one lon.

Any idea?

Thanks!

Answer 1

[Vedant Shah]

Hi @Pepe Grillo,

To extract data along a diagonal path from one GPS point to another and to plot how the data changes along that path at a specific time and depth, the following line of code does not work as it will give a straight slice at 'lon = 50' instead of a diagonal path.

ud = squeeze(u1(50,:,:,:)); 

The interpolation method needs to be used to get a diagonal path. So, initially the diagonal path needs to be defined and then a 2D slice needs to be extracted from the 4D array at a fixed time and depth. To get the values along the diagonal path, ‘interp2’ function can be used.

The following sample code demonstrates the above solution:

u1 = rand(241, 97, 1, 1637)

% Define grid 
lon = 1:241; 
lat = 1:97; 

% Define diagonal path 
lon_path = linspace(10, 70, 100); 
lat_path = linspace(10, 70, 100); 

% Select depth and time index 
d = 1; t = 1; 
slice = squeeze(u1(:, :, d, t)); 

% Create meshgrid for interpolation 
[LonGrid, LatGrid] = meshgrid(lon, lat); 

% Transpose slice to match meshgrid orientation 
slice = slice'; 

% Interpolate along the diagonal path 
interp_vals = interp2(LonGrid, LatGrid, slice, lon_path, lat_path); 

% Plot the result 
plot(interp_vals, 'LineWidth', 2); 

The result obtained using the above code for the mentioned sample values is as below:

For more information, refer to the following documentation:

• https://www.mathworks.com/help/matlab/ref/double.linspace.html
• https://www.mathworks.com/help/matlab/ref/meshgrid.html
• https://www.mathworks.com/help/matlab/ref/interp2.html