[ncl-talk] How to correct the co ordinates?

[Mary Haley]

Ipshita,

It just occurred to me that perhaps the "#" operator is not want you want.
This is for a matrix product, and has a very different meaning than simple
matrix multiplication.

If you are trying to multiply two arrays together, and one is a subset in
size of the other, as is the case with your arrays, then you want to use
"conform" to conform the smaller array to the larger array, and then do the
multiplication.  It would look like this:

      B = conform(sce,sce_area,(/1,2/)) * sce

Or do you really need to do a matrix product? If so, then the original code
that you had with the loop is correct. My "improvement" was wrong.

--Mary


On Tue, Mar 1, 2016 at 11:39 AM, Ipshita Majhi <ipmajhi at alaska.edu> wrote:

> HI Mary,
>
> Thank you for the input. Here are the printVarSummary of the two
> variables. When I multiply the two variables I get this
>
>
> *************************************************************************************
> fatal:Mat: One of the operands exceeds the rank of 2, can't continue
>
> *************************************************************************************
> Variable: sce
> Type: byte
> Total Size: 19259328 bytes
>             19259328 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 2487] x [lat | 88] x [lon | 88]
> Coordinates:
>             time: [7..17409]
> Number Of Attributes: 10
>   lon2d : <ARRAY of 7744 elements>
>   lat2d : <ARRAY of 7744 elements>
>   long_name : NOAA/NCDC Climate Data Record of snow cover extent
>   standard_name : surface_snow_binary_mask
>   grid_mapping : coord_system
>   coordinates : longitude latitude time snow_cover_threshold
>   valid_range : ( 0, 1 )
>   flag_values : ( 0, 1 )
>   flag_meanings : no_snow snow_covered
>   _FillValue : -9
> (0) 2487
> (1) 6
>
>
> ***********************************************************************************
> Variable: sce_area
> Type: float
> Total Size: 30976 bytes
>             7744 values
> Number of Dimensions: 2
> Dimensions and sizes: [rows | 88] x [cols | 88]
> Coordinates:
> Number Of Attributes: 7
>   long_name : cell area in km^2
>   standard_name : cell_area
>   grid_mapping : coord_system
>   coordinates : longitude latitude
>   units : km^2
>   valid_range : ( 10676.8, 41804.6 )
>   _FillValue : -999.9
>
>
> *********************************************************************************
>
>
>
> On Tue, Mar 1, 2016 at 7:39 AM, Mary Haley <haley at ucar.edu> wrote:
>
>> You didn't actually state what the problem was, so I guess you meant to
>> say that the plot is incorrect?
>>
>> You didn't provide any information about your data.  As we tell users
>> frequently, use "printVarSummary" to help us see what what your variables
>> look like:
>>
>> printVarSummary(B)
>>
>> You shouldn't need to allocate space for B and then fill it. Try
>> replacing this code:
>>
>>    B = new((/2487,88,88/),float)
>>    do i = 0,2486
>>       B(i,:,:)=sce(i,:,:)#sce_area(:,:)
>>    end do
>>
>> with:
>>
>> sce_area_3d = conform_dims(dimsizes(sce),sce_area,(/1,2/))
>> B           = sce # sce_area_3d
>>
>> One idea for the plot: maybe you need to turn off the addition of a
>> cyclic point:
>>
>> res at gsnAddCyclic = False
>>
>> If none of this helps, then please include output from "printVarSummary"
>> of all your variables.
>>
>> Thanks,
>>
>> --Mary
>>
>>
>> On Mon, Feb 29, 2016 at 12:12 PM, Ipshita Majhi <ipmajhi at alaska.edu>
>> wrote:
>>
>>> Dear NCL,
>>>
>>> I want to plot snow cover extent after multiplying it with snow cover
>>> area. Here is the code for it. I am also attaching the figure with this
>>> email.
>>>
>>> ;*******************************************
>>> ;Reading in the weekly snow cover extent
>>> ;*******************************************
>>>
>>> a=addfile("~/Documents/NCL_files/Sea_ice/
>>> nhsce_v01r01_19661004_20140602.nc","r")
>>> sce=a->snow_cover_extent ; The values are either 0 or 1
>>>
>>> lat=a->latitude
>>> lon=a->longitude
>>>
>>> sce!1="lat"
>>> sce!2="lon"
>>>
>>> sce at lat2d=lat
>>> sce at lon2d=lon
>>>
>>> ;********************************************
>>> :Reading in the snow cover are
>>> ;********************************************
>>>
>>> sce_area=a->area
>>>
>>> sce_area!0="lat"
>>> sce_area!1="lon"
>>>
>>> copy_VarAtts(sce,sce_area)
>>> copy_VarCoords_1(sce,sce_area)
>>>
>>> ;*******************************************
>>> ;Muliplying Snow cover extent and Area
>>> ;*******************************************
>>>
>>> B = new((/2487,88,88/),float)
>>>
>>>      do i = 0,2486
>>>       B(i,:,:)=sce(i,:,:)#sce_area(:,:)
>>>       end do
>>>
>>> B!0="time"
>>> B!1="lat"
>>> B!2="lon"
>>>
>>> B at lat2d=lat
>>> B at lon2d=lon
>>>
>>> copy_VarAtts(sce,B)
>>> copy_VarCoords_1(sce,B)
>>>
>>> printVarSummary(B)
>>>
>>> B at _FillValue = -9
>>>
>>>
>>> ;************************************************
>>> ; create plot
>>> ;************************************************
>>>   wks = gsn_open_wks("pdf" ,"Snow_cover_area")
>>>   res            = True                          ; plot mods desired
>>>   res at gsnPolar   = "NH"                          ; specify the
>>> hemisphere
>>>   plot = gsn_csm_contour_map_polar(wks,B(0,:,:),res)    ; create the plot
>>>
>>>
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>>>
>>>
>>
>
>
> --
> Ipshita Majhi
> PhD Candidate
> University of Alaska , Fairbanks
> Atmospheric Science Department
> (907)978-4220 ipmajhi at alaska.edu
>
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