Unrecognized function or variable

I'm having a problem where whenever I try to assign a function to a variable it says its an "Unrecognized function or variable" although its defined in my code. The code is below:

t = 1:1:2960;
t2= t/128;
t2 = t2';

%rc is raw data
%rcf is segmented data

fs = 128;
Lab5 = lowpass(realLab5.LEDC2,20,fs);
Lab5c= Lab5(116:2960);
m=1;
n=length(Lab5c);
for i = 2:n-1
    if Lab5c(i)>Lab5c(i-1) && Lab5c(i)>=Lab5c(i+1) && Lab5c(i)> 488000
        val(m) = Lab5c(i);
        pos1(m) = i;
        m = m+1;
    end
end

ppg_peaks = m-1;
ppg_pos = pos1(m);
ppg_val = val;

The error is :

Unrecognized function or variable 'pos1'.

Error in Heart_Rate (line 22)

ppg_pos = pos1(m);

[Walter Roberson]

By the way, you might want to consider using findpeaks with the minimum peak prominence option

Answer 1

[Voss]

if Lab5c(i)>Lab5c(i-1) && Lab5c(i)>=Lab5c(i+1) && Lab5c(i)> 488000

If that condition is never true then the block inside will never be executed

val(m) = Lab5c(i);

pos1(m) = i;

m = m+1;

So pos1 and val will be undefined after the loop ends and m will still be 1.

Answer 2

[Image Analyst]

Try this:

t = 1:1:2960;
t2= t/128;
t2 = t2';

%rc is raw data
%rcf is segmented data

fs = 128;
Lab5 = lowpass(realLab5.LEDC2,20,fs);
Lab5c= Lab5(116:2960);
m=1;
n=length(Lab5c);
% Assign nans to pos1:
pos1 = nan(1, n);
for i = 2:n-1
    if Lab5c(i)>Lab5c(i-1) && Lab5c(i)>=Lab5c(i+1) && Lab5c(i)> 488000
        val(m) = Lab5c(i);
        pos1(m) = i;
        m = m+1;
    end
end
% Alert user if no element of pos1 ever got assigned.
if all(isnan(pos1))
    warningMessage = sprintf('No element of pos1 ever got assigned!!!')
    uiwait(warndlg(warningMessage));
end
ppg_peaks = m-1;
ppg_pos = pos1(m);
ppg_val = val;

Set a breakpoint on the pos1(m)=1 line and see if it ever gets there (it won't). See this link:

Debugging in MATLAB | Doug's MATLAB Video Tutorials