How to crop the region in PyGMT?

Q&A PyGMT Q&A
1

I’m plotting a map of great circle ray paths from set of co-ordinates to another set, so initially I’m assigning a region to the grid. In the final output I need the same result but just for subset of the region/cropping the map to a new region within the grid. How should I approach this?

2

Repeat the first plot call with the new « region » (with a shift of the picture of course)?

3

Actually I’m unable to dow that, once after the things get plotted and I crop it to new region the great circle lines are disappearing because the cropped region I’m interested in doesn’t contain the other end of co-ordinates which form the ray paths

4

Hello @anirudh,

Welcome to the GMT forum :slightly_smiling_face:!

Unfortunately, I am having difficulty understanding your issue. I feel it would helpful if you could provide a code example demonstrating your issue.

Based on your last post, it sounds a bit like setting the no_clip parameter of Figure.plot to True could be helpful for you. However, no_clip actually does not apply to lines and polygons (for GMT 6.4.0, https://docs.generic-mapping-tools.org/6.4/plot.html#n).

5

Maybe OP doesn’t know how to play with -Bafg parameters in python ?

6

Actually I’m new to PyGMT itself and not well versed in GMT. Yeah I will provide you the example code

import numpy as np
import pygmt
import pandas as pd

fig = pygmt.Figure()

grid = pygmt.datasets.load_earth_relief(resolution="10m", region = [lat1, lon1, lat2, lon2])
fig.grdimage(grid=grid, projection="M15c", frame="a", cmap="geo")

#reading excel file
for i in range(0, len(rows)): #plotting ray paths
            if df.Final[i] == 'yes':
                point_1 = []
                point_1.insert(0, df.Lon[i])
                point_1.insert(1, df.Lat[i])
                main_point = main_cord[j]
                data = np.array([point_1 + main_point])
                fig.plot(data=data, style="=1c+a+s", pen="1p,red", fill="red3")

fig.show()

Like this is the code format so after the ray paths are plotted I need canvas to show me only the desired region extent which is
region2 = [lat’1, lon’1, lat’2, lon’2]

But,

  1. I’m unable to specify the fig to the region2 at end of the code - Its just overlaying new grid on the original region.
  2. If I specify region2 directly in the beginning of the code, ray path vectors are not plotted as the other set of co-ordinates exist outside region2
7

@anirudh thanks providing an code example!

Can you please try option 2 together with setting the no_clip parameter to True in fig.plot:

fig.plot(data=data, style="=1c+a+s", pen="1p,red", fill="red3", no_clip=True)

If this dose not fix your issue we also need your input data (i.e., what is read into the pandas DataFrame df) to have a more detailed look at your problem.

One comment regarding your study area set via the region parameter: You have to give it in the order lon1, lon2, lat1, lat2.

1 Like
9

Thank you very much, no_clip=True worked