DKRZ PyNGL panel with vp resources example#
Example script:
#----------------------------------------------------------------------
# DKRZ PyNGL Script: panel_vp.py
#
# Description: Creates a panel plot using the vp-resources instead
# of the PyNGL function Ngl.panel.
#
# Output: plot_panel_vp.png
#
# 28.10.19 meier-fleischer(at)dkrz.de
#----------------------------------------------------------------------
import sys
import os
import numpy as np
import xarray as xr
import Ngl
#----------------------------------------------------------------------
# Based on add_lon_labels from PyNGL example spaghetti.py.
# -- The labels won't fit perfectly when mpCenterLonF is used.
# This procedure adds longitude labels to the outside of a circular
# polar stereographic map.
#----------------------------------------------------------------------
def add_lon_labels(wks,map,res):
'''
Function add_lon_labels(wks, map, res)
This procedure adds longitude labels to the outside of a circular
polar stereographic map.
List the longitude values where you want labels. It's assumed that
longitude=0 is at the bottom of the plot, and 180W at the top. You can
adjust as necessary.
'''
lon_values = np.arange(-180,180,30)
nlon = lon_values.shape[0]
lat_values = np.zeros(nlon,'f') + res.mpMinLatF
#-- Get the NDC coordinates of these lat,lon labels. We'll use this information
#-- to place labels *outside* of the map plot.
xndc, yndc = Ngl.datatondc(map,lon_values,lat_values)
#-- Set an array of justification strings to use with the 'txJust' resource
#-- for each label, based on which quadrant it appears in.
just_strs = ['BottomCenter', #-- top of plot
'BottomRight','BottomRight', #-- upper left quadrant
'CenterRight', #-- left of plot
'TopRight','TopRight', #-- lower left quadrant
'TopCenter', #-- bottom of plot
'TopLeft','TopLeft', #-- lower right quadrant
'CenterLeft', #-- right of plot
'BottomLeft','BottomLeft'] #-- upper right qudrant
#-- Create an array of longitude labels with 'W' and 'E' added.
lon_labels = []
for i in range(nlon):
if lon_values[i] == -180:
lon_labels.append('{:g}W ~C~ '.format(abs(lon_values[i]))) #-- move the label upward
elif lon_values[i] < 0:
lon_labels.append('{:g}W '.format(abs(lon_values[i]))) #-- add W and move to the left
elif lon_values[i] > 0:
lon_labels.append(' {:g}E'.format(lon_values[i])) #-- add E and move to the right
else:
lon_labels.append(' ~C~{:g}'.format(lon_values[i])) #-- move label downward
#-- Loop through each label and add it.
txres = Ngl.Resources()
txres.txFontHeightF = 0.01
for i in range(nlon):
txres.txJust = just_strs[i]
Ngl.text_ndc(wks,lon_labels[i],xndc[i],yndc[i],txres)
return
#-- main function
def main():
fname = 'rectilinear_grid_2D.nc' #-- file name
ds = xr.open_dataset(fname) #-- open file
#-- define the contour minimum, maximum, and increment
minval = 250. #-- minimum contour level
maxval = 315. #-- maximum contour level
inc = 5. #-- contour level spacing
ncn = (maxval-minval)/inc + 1 #-- number of contour levels.
#-- define contour levels, labels, and colors
levels = np.arange(minval,maxval,inc)
labels = [str(s) for s in levels]
colors = np.arange(10,250,10)
#-- generate a res object for workstation and open it
wkres = Ngl.Resources()
wkres.wkColorMap = "ncl_default"
wks = Ngl.open_wks('png','plot_panel_vp',wkres)
#-- set resources
res = Ngl.Resources() #-- plot mods desired
res.nglDraw = False #-- don't draw until the end
res.nglFrame = False #-- don't automatically advance frame
res.nglMaximize = False #-- don't maximize the plot, we want to
#-- use viewport settings
res.vpXF = 0.05 #-- viewport x-position
res.vpYF = 0.94 #-- viewport y-position
res.vpWidthF = 0.37 #-- viewport width
res.vpHeightF = 0.37 #-- viewport height
res.mpProjection = 'Stereographic'#-- set map projection
res.mpEllipticalBoundary = True #-- map projection area is limited to an ellipse
#-- inscribed within the normal rectangular
#-- perimeter of the viewport
res.mpDataSetName = 'Earth..4' #-- change map data set
res.mpDataBaseVersion = 'MediumRes' #-- choose higher map resolution
res.mpLimitMode = 'LatLon'
res.mpMaxLatF = 90. #-- maximum latitude; northern hemisphere
res.mpMinLatF = 30. #-- minimum latitude
res.mpCenterLatF = 90. #-- center latitude
res.pmTickMarkDisplayMode = 'Never' #-- turn off default ticmkark object,
#-- don't draw the box
res.cnFillOn = True #-- turn contour fill on
res.cnLinesOn = False #-- turn off contour lines
res.cnLineLabelsOn = False #-- turn off contour line labels
res.cnInfoLabelOn = False #-- turn off contour line info label
res.cnLevelSelectionMode = 'ManualLevels' #-- set manual levels
res.cnMinLevelValF = minval #-- minimum value
res.cnMaxLevelValF = maxval #-- maximum value
res.cnLevelSpacingF = inc #-- increment
res.lbLabelBarOn = False
#-- assign plot array
plot = []
#-- create the 4 plots
j = 0
for i in range(4):
var = ds.tsurf[j,:,:] #-- j. time step
var,lon = Ngl.add_cyclic(var,ds.lon) #-- add cyclic point to data array and longitude
res.sfXArray = lon #-- use cyclic longitude; already numpy array
res.sfYArray = ds.lat.values #-- use latitude in numpy array
res.tiMainString = 'time step: '+str(j)
res.tiMainOffsetXF = 0.02
res.tiMainOffsetYF = -0.01
res.tiMainPosition = 'Left'
#-- define position of the plots in the frame
if(i == 0 or i == 2):
res.vpXF = 0.08
else:
res.vpXF = 0.52
if(i == 0 or i == 1):
res.vpYF = 0.94
else:
res.vpYF = 0.5
plot.append(Ngl.contour_map(wks,var,res))#-- create contour plot
Ngl.draw(plot[i])
add_lon_labels(wks,plot[i],res) #-- add labels to map
j = j + 12 #-- increase time index
#-- add a common labelbar at the bottom
lbres = Ngl.Resources()
lbres.vpWidthF = 0.7
lbres.vpHeightF = 0.10
lbres.lbOrientation = 'Horizontal'
lbres.lbFillPattern = 'SolidFill'
lbres.lbMonoFillPattern = 21 #-- must be 21 for color solid fill
lbres.lbMonoFillColor = False #-- use multiple colors
lbres.lbFillColors = colors #-- indices from loaded colormap
lbres.lbLabelFontHeightF = 0.010
lbres.lbLabelAlignment = 'InteriorEdges'
lbres.lbLabelStrings = labels
lbres.lbTitleOn = True
lbres.lbTitleString = ds.tsurf.long_name + ' [' + ds.tsurf.units + ']'
lbres.lbTitlePosition = 'Bottom'
lbres.lbTitleFontHeightF = 0.016
lbx, lby = 0.15, 0.11
lb = Ngl.labelbar_ndc(wks, len(levels)+1, labels, lbx, lby, lbres)
#-- close the frame, write the graphic output to disk
Ngl.frame(wks)
#-- call main function
if __name__ == '__main__':
main()
Result:
