[Numpy-discussion] find location of maximum values

questions anon questions.anon@gmail....
Mon Jan 9 22:40:02 CST 2012


Thank you, thank you, thank you!
I needed to find the max value (and corresponding TIME and LAT, LON) for
the entire month but I shouldn't have been using the tmax, instead I needed
to use the entire array. Below code works for those needing to do something
similar.
Thanks for all your help everyone!


            tmax=TSFC.max(axis=0)
            maxindex=TSFC.argmax()
            maxtemp=TSFC.ravel()[maxindex] #or maxtemp=TSFC.max()
            print maxindex, maxtemp
            val=N.unravel_index(maxindex, TSFC.shape)
            listval=list(val)
            print listval
            timelocation=TIME[listval[0]]
            latlocation=LAT[listval[1]]
            lonlocation=LON[listval[2]]
            print latlocation, lonlocation
            cdftime=utime('seconds since 1970-01-01 00:00:00')
            ncfiletime=cdftime.num2date(timelocation)
            print ncfiletime


On Tue, Jan 10, 2012 at 3:28 PM, Aronne Merrelli
<aronne.merrelli@gmail.com>wrote:

>
>
> On Mon, Jan 9, 2012 at 7:59 PM, questions anon <questions.anon@gmail.com>wrote:
>
>> thank you, I seem to have made some progress (with lots of help)!!
>> I still seem to be having trouble with the time. Because it is hourly
>> data for a whole month I assume that is where my problem lies.
>> When I run the following code I alwayes receive the first timestamp of
>> the file. Not sure how to get around this:
>>
>>             tmax=TSFC.max(axis=0)
>>             maxindex=tmax.argmax()
>>
>
> You are computing max(axis=0) first. So, tmax is an array containing the
> maximum temperature at each lat/lon grid point, over the set of 721 months.
> It will be a [106, 193] array.
>
> So the argmax of tmax is an element in a shape [106,193] array (the number
> of latitude/number of longitude) not the original three dimension [721,
> 106, 193] array. Thus when you unravel it you can only get the first time
> value.
>
> I re-read your original post but I don't understand what number you need.
> Are you trying to get the single max value over the entire array? Or max
> value for each month? (a 721 element vector)? or something else?
>
>
> Cheers,
> Aronne
>
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>
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