DKRZ PyNGL map tickmark example with gridlines#
Example script:
#
# File:
# mptick_5.py
#
# Synopsis:
# Demonstrates how to change the tickmark label font height, adjust
# the tickmark length, and turn on grid lines (a map resource).
#
# Categories:
# map plot
# grid lines
# annotation
#
# Based on NCL example:
# mptick_5.ncl
#
# Author:
# Karin Meier-Fleischer
#
# Date of initial publication:
# November 2018
#
# Description:
# This example shows how to create a map.
#
# Effects illustrated:
# o Decreasing the size of tickmark labels
# o Changing the length of tickmarks
# o Turning on map grid lines
#
# Output:
# A single visualization is produced.
#
'''
PyNGL Example: mptick_5.py
- Decreasing the size of tickmark labels
- Changing the length of tickmarks
- Turning on map grid lines
'''
from __future__ import print_function
import numpy as np
import Ngl
#-----------------------------------------------------------------------
#-- Function: main
#-----------------------------------------------------------------------
def main():
lat_spacing = 30 #-- y-axis label increment
lon_spacing = 30 #-- x-axis label increment
wks = Ngl.open_wks("png","plot_mptick_5") #-- open workstation
mpres = Ngl.Resources() #-- resource object
mpres.nglDraw = False #-- Don't draw map
mpres.nglFrame = False #-- Don't advance frame
mpres.mpFillOn = True #-- turn map fill on
mpres.mpOutlineOn = False #-- outline map
mpres.mpOceanFillColor = "Transparent" #-- set ocean fill color to transparent
mpres.mpLandFillColor = "Gray90" #-- set land fill color to gray
mpres.mpInlandWaterFillColor = "Gray90" #-- set inland water fill color to gray
mpres.mpProjection = "CylindricalEquidistant" #-- map projection
mpres.mpGridAndLimbOn = False #-- turn off grid lines
mpres.pmTickMarkDisplayMode = "Never" #-- turn on built-in tickmarks
map = Ngl.map(wks,mpres) #-- create the base plot
#-- create x-axis labels starting with 150 degrees west, every 50th degrees
lon_values = np.arange(-180.0,211.0,lon_spacing)
lon_labels = []
for l in lon_values:
if l < 0:
lon_labels.append("{}~S~o~N~W".format(np.fabs(l)))
elif l > 0:
lon_labels.append("{}~S~o~N~E".format(l))
else:
lon_labels.append("0")
#-- create y-axis labels starting with 80 degrees south, every 20th degrees
lat_values = np.arange(-90.0,101.0,lat_spacing)
lat_labels = []
for l in lat_values:
if l < 0:
lat_labels.append("{}~S~o~N~S".format(np.fabs(l)))
elif l > 0:
lat_labels.append("{}~S~o~N~N".format(l))
else:
lat_labels.append("0")
#-- new resources for the blank plot
bres = Ngl.Resources()
bres.nglMaximize = False
bres.nglPointTickmarksOutward = True #-- tick marks outside
bres.vpXF = Ngl.get_float(map,"vpXF")
bres.vpYF = Ngl.get_float(map,"vpYF")
bres.vpWidthF = Ngl.get_float(map,"vpWidthF")
bres.vpHeightF = Ngl.get_float(map,"vpHeightF")
bres.trXMinF = Ngl.get_float(map,"trXMinF")
bres.trXMaxF = Ngl.get_float(map,"trXMaxF")
bres.trYMinF = Ngl.get_float(map,"trYMinF")
bres.trYMaxF = Ngl.get_float(map,"trYMaxF")
bres.tmXBMode = "Explicit" #-- use explicit x-axis values and labels
bres.tmXBValues = lon_values #-- x-axis values
bres.tmXBLabels = lon_labels #-- x-axis labels
bres.tmXBLabelFontHeightF = 0.013 #-- smaller x-axis labels
bres.tmXBMajorLengthF = 0.01 #-- change the tickmark length
bres.tmYLMode = "Explicit" #-- use explicit y-axis values and labels
bres.tmYLValues = lat_values #-- y-axis values
bres.tmYLLabels = lat_labels #-- y-axis labels
bres.tmYLLabelFontHeightF = 0.013 #-- smaller y-axis labels
bres.tmXMajorGrid = True #-- x-axis turn on grid lines
bres.tmXMajorGridLineDashPattern = 2 #-- x-axis grid line dash pattern
bres.tmYMajorGrid = True #-- y-axis turn on grid lines
bres.tmYMajorGridLineDashPattern = 2 #-- y-axis grid line dash pattern
#-- create a blank plot with the axes annotations
blank = Ngl.blank_plot(wks,bres)
#-- attach the blank plot to the map
sres = Ngl.Resources()
sres.amZone = 0 #-- '0' means centered over base plot
sres.amResizeNotify = True #-- adjust size of plot to base plot
Ngl.add_annotation(map,blank,sres)
#-- maximize the plot, draw the plot, and advance the frame
Ngl.maximize_plot(wks,map) #-- maximize the map plot
Ngl.draw(map)
Ngl.frame(wks)
Ngl.end()
if __name__ == '__main__':
main()
Result:
