Mtalab code Histogram Data Variation

% Read ECG for the last data from a ThingSpeak channel and 
% visualize temperature variations using the MATLAB HISTOGRAM function. 
   
% Channel (ID: 1283400) contains data from the MathWorks Weather Station, located 
% in Sfax, Tunisia. The data is collected once for diver laps of time.
%Field 1 contains Signal data (each 15seconds).

% Channel ID to read data from 
readChannelID = 1283400; 
   
% Field ID 
EcgFieldID = 1; 

%Number of recods to read (lines)
points= 1000;

% Channel Read API Key   
% If your channel is private, then enter the read API 
% Key between the '' below:   
readAPIKey = ''; 

% Get temperature data from field 4 for the  
% minutes. Learn more about the THINGSPEAKREAD function by going to 
% the Documentation tab on the right side pane of this page. 
   
ecgH = thingSpeakRead(readChannelID,'Fields',EcgFieldID,...
                                    'NumPoints',points,  ...
                                    'ReadKey',readAPIKey); 
                       %'NumMinutes',10*60 % last 10 hours = 10 x 60
   
histogram(ecgH); 
xlabel('ECG (mV)'); 
ylabel('Number of Measurements\newline for Each signal measure'); 
title('Histogram of ECG Variation');