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# PyNGL example rectilinear slice plot

The script creates a slice contour plot of rectilinear gridded data.

Software requirements:

• Python 2.7.x
• Numpy 1.9.2
• PyNGL/PyNIO 1.5.0

Run the rectilinear slice contour example script:

`python PyNGL_rectilinear_slice.py`

Script PyNGL_rectilinear_slice.py:

```'''
DKRZ PyNGL Script: PyNGL_rectilinear_slice.py

Description:       Python script using PyNGL Python module
- slice plot at lat index=69 (rectilinear data)

2015-06-04  meier-fleischer(at)dkrz.de
'''
import numpy,sys,os
import Ngl,Nio

#--  define variables
diri   = "./"                                  #-- data directory
fname  = "rectilinear_grid_3D.nc"              #-- data file name

#--  open file and read variables
f      =  Nio.open_file(diri + fname,"r")      #-- open data file
t      =  f.variables["t"][0,:,::-1,:]         #-- first time step, reverse latitude
t70    =  t[:,69,:]                            #-- variable at lat index 69
lev    =  f.variables["lev"][:]                #-- all levels
lat    =  f.variables["lat"][::-1]             #-- reverse latitudes
lon    =  f.variables["lon"][:]                #-- all longitudes
nlat   =  len(lat)                             #-- number of latitudes

strlat70 = lat[69]                             #-- retrieve data of lat array index 69

#-- get the minimum and maximum of the data
minval =  int(numpy.amin(t))                   #-- minimum value
maxval =  int(numpy.amax(t))                   #-- maximum value
inc    =  5                                    #-- contour level spacing
ncn    =  (maxval-minval)/inc + 1              #-- number of contour levels

#-- open a workstation
wkres                     =  Ngl.Resources()   #-- generate an res object for workstation
wkres.wkWidth             =  1024              #-- plot resolution 2500 pixel width
wkres.wkHeight            =  1024              #-- plot resolution 2500 pixel height
wks_type                  = "png"              #-- output type
wks                       =  Ngl.open_wks(wks_type,"Py_rectilinear_slice",wkres)  #-- open workstation

#-- set resources
res                       =  Ngl.Resources()   #-- generate an res object for plot
res.tiMainString =  f.variables["t"].long_name + " at lat " + "{:.2f}".format(strlat70) + " degrees"
#-- set main title
#-- viewport resources
res.vpXF                  =  0.1               #-- start x-position of viewport
res.vpYF                  =  0.9               #-- start y-position of viewport
res.vpWidthF              =  0.7               #-- width of viewport
res.vpHeightF             =  0.7               #-- height of viewport

#-- contour resources
res.cnFillOn              =  True              #-- turn on contour fill
res.cnLineLabelsOn        =  False             #-- turn off line labels
res.cnInfoLabelOn         =  False             #-- turn off info label
res.cnLevelSelectionMode  = "ManualLevels"     #-- select manual levels
res.cnMinLevelValF        =  minval            #-- minimum contour value
res.cnMaxLevelValF        =  maxval            #-- maximum contour value
res.cnLevelSpacingF       =  inc               #-- contour increment

#-- grid resources
res.sfXArray              =  lon               #-- scalar field x
res.sfYArray              =  lev               #-- scalar field y

#-- labelbar resources
res.pmLabelBarDisplayMode = "Always"           #-- turn off the label bar

#-- draw slice contour plot
plot = Ngl.contour(wks,t70,res)

#-- done
Ngl.end()```

Plot result:

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