Run a code multiple times and save variables

Hi,

I would like to run the following code every 20 seconds for 5 minutes in order to get the latest bitcoin price.

rawdata = urlread('https://www.bitstamp.net/api/ticker/');

j = strfind(rawdata, 'high');
k = strfind(rawdata, 'last');
m = strfind(rawdata, 'vwap');
o = strfind(rawdata, 'volume');
p = strfind(rawdata, 'low');

High=rawdata(j+8:j+13);
Last=rawdata(k+8:k+13)
vwap=rawdata(m+8:m+13);
volume=rawdata(o+10:o+22);
low=rawdata(p+7:p+12);

I would like the value of high/last/vwap etc for each of the time periods. I am having trouble using a vector as I don't know if urlread can be used in this format.

Any help would be much appreciated.

Thanks,

Stu

Answer 1

[dpb]

M=5;            % number of minutes
P=20;           % period between readings
N=60/P*M;       % readings expected
% format string for the data line returned...
fmt=['{"high": "%f", "last": "%f",' repmat('%*s ',1,4) '"vwap": "%f", "volume": "%f", "low": "%f"']
data=zeros(N,5); % preallocate
for i=1:N
  rawdata=urlread('https://www.bitstamp.net/api/ticker/');
  data(i,:)=sscanf(rawdata,fmt).';
  pause(P)
end

Your values will be

High Last VWAP Vol Low

by column for each period.

[Stuart]

Thanks for answering so quick.Its much appreciated. When I run the above I receive the following error:

??? Subscripted assignment dimension mismatch.

Error in ==> dpb at 12
  data(i,:)=sscanf(fmt,rawdata)';

Do you know why?

Thanks,

Stu

[dpb]

Check on rawdata being valid and what does

sscanf(fmt,rawdata)'

return at the command line?

Here with a sample line downloaded I get

>> rawdata
rawdata =
{"high": "635.00", "last": "633.00", "timestamp": "1405114465", "bid": "633.00", "vwap": "625.52", "volume": "6238.10039398", "low": "613.46", "ask": "634.78"}
>> sscanf(rawdata,fmt).'
ans =
 1.0e+03 *
  0.6350    0.6330    0.6255    6.2381    0.6135

Ewww.... :( My bad, somehow what I posted here has the arguments to sscanf reversed--should be

data(i,:)=sscanf(rawdata,fmt).';

I edited Answer to make the correction.

[Stuart]

Thanks dpb.

Much appreciated.

[dpb]

No problem...you'll undoubtedly want to add some error handling and all...the pause is klunky; not sure whether there's a way to schedule it as a callback or not--never investigated that in Matlab.