finding size of arrays in nested structs

I have been searching for the answer to this for a couple of days and haven't had any luck.

I have a data structure that includes another layer of structures, each of which includes multiple arrays:

Blck (1x1 struct)

   epocs (1x1 struct)
   snips (1x1 struct)
   streams (1x1 struct)
      Stim (1x1 struct)
         data (16x2655114 single)
         fs (2.4414e+04)
         name ('stim')
      Sign (1x1 struct)
      EMGX (1x1 struct)
      EMGR (1x1 struct)
        .
        .
        .

I need to find the size of the array 'data'.

I have tried:

size(Blck.streams.Stim.data)

and I get the correct answer:

 ans=16 2655114

but when I try to find the size in a loop I get the wrong answer:

size(strcat('Blck.streams.',SelectedStreams(StreamIndex),'.data'))

I get:

ans=1 1

I realized that

strcat('Blck.streams.',SelectedStreams(StreamIndex),'.data')
='Blck.streams.Stim.data'

so I tried:

    Streams=SelectedStreams(StreamIndex)

    size(sprintf('Blck.streams.%s.data',Streams))

Which yielded:

ans= 1 22

I don't know where that came from.

What I need is to find the size of Blck.streams.Stim.data, which should be:

ans=16 2655114

What command should I be using inside a loop that goes through all the streams and finds the size of the data arrays?

[Doug Hull]

Can you show us the structure in simpler form?

a.b(1).c = [1 2; 3 4; 5 6]
a.b(2).c = [1; 2]
size(a.b(1).c)
size(a.b(2).c)

Or something similar so we are all working on the same structure and you can specifically show us what you are looking for?

[Noel]

Blck.streams.Stim.data=[an array with 16 rows and over 2 million columns]

Blck.streams.EMGx.data=[an array with 16 rows and over 300,000 columns]

Blck.streams.ECGx.data=[an array with 1 row and over 100,000 columns]

Blck.streams.ACCx.data=[an array with 4 rows and over 30,000 columns]

basically, this is electrophysiology data produced by a data acquisition system that has inputs with different sampling rates. I am trying to figure out how to display each variable time locked to the Stim stream. I am to the point where I can display the plots individually, but now I am trying to set up a loop that displays all the selected variables in subplots. I need to know the number of rows because that represents the number of data channels. (I don't need to plot all 16 channels of EMGx data, only the last 4 are actually being used for measurement).

Answer 1

[Matt J]

For example, the following is equivalent to size(Blck.streams.EMGx.data),

    SelectedStreams={'Stim','EMGx','ECGx','ACCx'};

    StreamIndex=2;

    size(Blck.streams.(SelectedStreams{StreamIndex}).data)

[Noel]

Awesome, curly brackets always get me.

Worked great!

Noel