# Re: [Discuss-gnuradio] Trouble decimating after averaging 4 vectors? Help?

Thanks Jeff,

I’ll give that a try.

I think I’m also missing something that tells gnu radio what the expected
decimation is (?),
beyond the decimate = 4 parameter(?).

Also concerning your point, then if I have a non-multiple of 4 vectors I guess
I need
to keep the sum and count, but I guess that is already a part of the code.

Best regards

Glen

> On Mar 11, 2018, at 3:54 PM, Jeff Long <willco...@gmail.com> wrote:
>
> in[0] is not the first vector, it is all of the available input for port 0.
> So, you feed in 4 vectors in your test program, and the shape of in[0] is
> (4,1024). You're missing a loop that iterates over the input vectors.
>
> On 03/11/2018 02:06 PM, Glen I Langston wrote:
>> I'm following the gnuradio tutorial for creating an out of tree python block.
>> My intention is fairly simple.  To have a input stream of 4 vectors
>> and average these 4 vectors, outputting a single average vector
>> after the 4th vector arrives.  Right now my vectors are 1024 channel
>> total power spectra.
>> My code is attached, along with the quality control code.
>> I've been at this for a while, but I must have the wrong model
>> I'm not getting the proper size matches.   I can not find any
>> decimation help, despite hours of googling...
>> Suggestions?
>> THanks
>> Glen
>> My intention is to make this 4 vector average with decimate a
>> part of the .grc environment, but the problems are easier to diagnose,
>> as the QA code is stands alone.   Here are the messages I’m getting:
>> ESMU:vdecimate glangsto\$ python qa_vdecimate.py
>> handler caught exception: could not broadcast input array from shape
>> (4,1024) into shape (1,1024)
>> Traceback (most recent call last):
>>   File
>>  line 55, in eval
>>     try: self._callback()
>>   File
>>  line 160, in __gr_block_handle
>>     ) for i in self.__out_indexes],
>>   File "/Users/glangsto/Desktop/Research/vdecimate/vdecimate.py", line 58,
>> in work
>>     out[:] = self.sum/float(self.count)
>> ValueError: could not broadcast input array from shape (4,1024) into shape
>> (1,1024)
>> error. Error detected when calling 'feval_ll.eval'
>> _______________________________________________