Re: create array of max value in vertical for multi-dimensional array

Oops, I made a mistake. The function input is x(jj,:,:,:). This
reduces the 4-D array to 3-D before the function sees it. Therefore
the dimension over which to find the maximum becomes #0, not #1.

    dim_level = 0
    maxZ = dim_max_n (x (jj,:,:,:), dim_level)

Also see Dennis's answer if you want to find each maximum over 2
dimensions at the same time, rather than 1.

--Dave

On Mon, Jan 9, 2012 at 11:28 PM, Dave Allured <dave.allured@noaa.gov> wrote:
> So you are inside a loop over jj, and you want to repeat this
> calculation for each jj?  In other words, you want a 2-D result, but
> you want to repeat that 2-D result for the number of time steps?
>
> If so, I think you want this inside the time loop. Note that maxZ will
> be overwritten with new values on each iteration:
>
> dim_level = 1
> maxZ = dim_max_n (x (jj,0:29,:,:), dim_level)
>
> Or perhaps this would be simpler if you are not really trying to
> constrain to the first 30 levels:
>
> dim_level = 1
> maxZ = dim_max_n (x (jj,:,:,:), dim_level)
>
> Reference:
> http://www.ncl.ucar.edu/Document/Functions/Built-in/dim_max_n.shtml
>
> --Dave
>
> On Mon, Jan 9, 2012 at 10:14 PM, Chris Herbster <herbstec@erau.edu> wrote:
>> Hi folks,
>>
>> I may have tried the wrong search terms while looking for this in the
>> archives, but perhaps I can get a quick solution to my quest.
>>
>> I would like to obtain the max value at each horizontal point in a
>> multi-dimensional array for each time.
>>
>> The array is x(time,level,lat,lon) and I am looking for the max value
>> for a given time (set with an index value) for each lat/lon location.
>> Obviously when I use the max function on the array I get a scalar
>> result.  I'd like the scalar result for each location in the horizontal.
>>
>> I want to obtain a 2D array out of a 4D array, but I have a loop (on jj)
>> that sets the time element to a specific index.  I tried:
>>
>> maxZ(:,:) = max (x (jj,0:29,:,:)
>>     where jj is a loop over the 24 hours, the second index is Z, the
>> range I want the max value out of, and the last two are the lat and long
>> index values.
>>
>> That gave an error about maxZ not existing.  Is the fix as simple as
>> creating the array with the correct dimensions?
>>
>> Of course when I tried to do this without an index placeholder then maxZ
>> is a scalar and I can't plot that on a map.
>>
>> I'm almost certain there is a way to do this without having nested loops
>> on the x and y variables.
>>
>> Thanks for the help!
>>
>> Chris Herbster
>>
>> --
>>
>>  Dr. Christopher G. Herbster
>>  Associate Professor
>>  Director of Science and Technology
>>  for the ERAU Weather Center
>>  Applied Aviation Sciences
>>  Embry-Riddle Aeronautical Univ.
>>  600 S. Clyde Morris Blvd.
>>  Daytona Beach, FL 32114-3900
>>
>>  386.226.6444 Office
>>  386.226.6446 Weather Center
>>  http://wx.erau.edu/
>>
>> Schedule at:  http://wx.erau.edu/faculty/herbster/Schedules/
>>
>> _______________________________________________
>> ncl-talk mailing list
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Tue Jan 10 12:01:42 2012