# [ncl-talk] slice plot

Bedassa Regassa beregassa at gmail.com
Tue Oct 7 06:34:43 MDT 2014

```It is perfect answer. It works!!
Bedassa

On Fri, Oct 3, 2014 at 12:10 AM, Dennis Shea <shea at ucar.edu> wrote:

> Some examples of what DaveB is talking about are at:
>
> ====
> https://www.ncl.ucar.edu/Applications/narr.shtml
> Examples 5 & 6
>
>
> NARR Example 5 uses a weight file generated by an ESMF Example 30
>   http://www.ncl.ucar.edu/Applications/ESMF.shtml
>
> =====
> http://www.ncl.ucar.edu/Applications/asr.shtml
> Examples 5 & 6
>
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
> NOTE: if you are 'new to NCL' ... PLEASE read documentation.
>
>  http://www.ncl.ucar.edu/Document/Manuals/
>
>  [1]  The "Mini-Language Manual" contains a detailed overview of the
> language
>
>  [2] THE DKRZ turotials are quite good.
>
>
>
> On Thu, Oct 2, 2014 at 3:56 PM, David Brown <dbrown at ucar.edu> wrote:
>
>> Hi Bedassa,
>>
>> You can't plot something with a 2D coordinate against a 1D coordinate in
>> a 2D plot. The lon2d gives the longitude values for a horizontal 2D field.
>> You have to make some choices to get a vertical plot -- you need to reduce
>> the latitude dimension to a single element somehow. The simplest thing to
>> do would be to just pick one index along the y axis of the lon coordinate
>> -- e.g. lon2d(100,:). However, because the coordinates are 2d, the chances
>> are that this would not be a constant latitude, so you could not say for
>> instance that your plot represents height vs longitude at 10 degrees North
>> latitude.
>>
>> But with proper labeling you could describe what this plot does
>> represent. I suggest you look at the NCL Examples page for Pressure/Height
>> vs Longitude plots and specifically at the last example on the page called
>> narr_6.ncl. It shows height plots for data where the coordinates are 2D
>> (aka "curvilinear" coordinates). Notice that the X axis for these plots has
>> both lat/lon values for the tickmark labels.This should give you some ideas
>> of what the issues are and how to solve them.
>>
>> Creating a plot where the latitude is constant would require a bit more
>> work. But if you wanted to try you would probably want to use the function
>> getind_latlon2d. This might actually be a good topic for a future example.
>>  -dave
>>
>>
>> On Wed, Oct 1, 2014 at 4:24 PM, Bedassa Regassa <beregassa at gmail.com>
>> wrote:
>>
>>> I am new to ncl. I am to plot the vertical Height vs longitude but I got
>>> warning and I tried to a lot to find my error.
>>>
>>> here is the wraning
>>>
>>> warning:ScalarFieldSetValues: 2d coordinate array sfXArray has an
>>> incorrect dimension size: defaulting sfXArray
>>>
>>> here is my data information ncl_filedump and below alos my scrip
>>>
>>> dimensions:
>>>       x = 186
>>>       y = 166
>>>       pressure = 9
>>>       time = 1  // unlimited
>>>       nb2 = 2
>>>    variables:
>>>       float lon ( y, x )
>>>          standard_name :        longitude
>>>          long_name :    longitude
>>>          units :        degrees_east
>>>          _CoordinateAxisType :  Lon
>>>
>>>       float lat ( y, x )
>>>          standard_name :        latitude
>>>          long_name :    latitude
>>>          units :        degrees_north
>>>          _CoordinateAxisType :  Lat
>>>
>>>       float pressure ( pressure )
>>>          standard_name :        air_pressure
>>>          long_name :    pressure
>>>          units :        Pa
>>>          positive :     down
>>>          axis : Z
>>>
>>>       double time ( time )
>>>          standard_name :        time
>>>          long_name :    time
>>>          bounds :       time_bnds
>>>          units :        seconds since 2009-05-01 00:00:00
>>>          calendar :     proleptic_gregorian
>>>
>>>       double time_bnds ( time, nb2 )
>>>          units :        seconds since 2009-05-01 00:00:00
>>>          calendar :     proleptic_gregorian
>>>
>>>  float U ( time, pressure, y, x )
>>>          standard_name :        grid_eastward_wind
>>>          long_name :    U-component of wind
>>>          units :        m s-1
>>>          coordinates :  lon lat
>>>
>>> ;************************************************
>>> ;************************************************
>>> ;************************************************
>>> begin
>>> ;************************************************
>>> ;open file and read in data
>>> ;************************************************
>>> ;************************************************
>>> ; get variables infromation and print them  cclm
>>> ;************************************************
>>> vars = getfilevarnames(f)
>>> print(vars)
>>> ;************************************************
>>> var=f->U(0,:,15,:)
>>> lon2d=f->lon
>>> lev=f->pressure
>>>
>>> var at lon2d=lon2d
>>> var at lev=lev
>>> ;*******************************
>>> ;create plot
>>> ;************************************************
>>>
>>> ;-- define workstation
>>> wks = gsn_open_wks("png","plot_slices")
>>> gsn_define_colormap(wks,"ncl_default") ;-- set the colormap to be used
>>> ;-- set resources
>>> res = True
>>> res at tiMainString = "DKRZ NCL Tutorial Example: Slice plot at 40N"
>>> res at cnFillOn = True ;-- turn on color fill
>>> res at cnLineLabelsOn = False ;-- turns off contour line labels
>>> res at cnInfoLabelOn = False ;-- turns off contour info label
>>> res at lbOrientation = "vertical" ;-- vertical label bar
>>> res at tiYAxisString = var at long_name+" [hPa]"
>>> ;-- append units to y-axis label
>>> ;res at tfDoNDCOverlay = True
>>> res at sfXArray = lon2d ;-- uses lon_t as plot x-axis
>>> res at sfYArray = lev/100 ;-- uses lev_t in hPa as plot y-axis
>>> res at gsnYAxisIrregular2Linear = True ;-- converts irreg depth to linear
>>> res at trYReverse = True ;-- reverses y-axis
>>>
>>> ;-- generate the plot
>>> plot = gsn_csm_contour(wks,var,res)
>>> end
>>>
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>>
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