I have a signal into which I want to introduce several offsets and delays, where offsets range from 0.5
to 5
and delays range from 1
to 7
.
I'm providing an example signal here to demonstrate the problem I'm having, but the size of my real data is 1x1666520.
How do I introduce these changes to the signal?
Example code:
t = [ 0 : 1 : 50]; % Time Samples
f = 45; % Input Signal Frequency
Fs = 440; % Sampling Frequency
data = sin(2*pi*f/Fs*t)';
T.InputOffset = 5;
T.OutputOffset = 5;
addoffset = retrend(data);
Y = step(delay,data);
figure(); plot(t,addoffset,t,Y);
When trying to run your example code, I'm getting this error:
Undefined function retrend
for input arguments of type double
.
The cause of this is that the retrend
function, which is part of the System Identification Toolbox, requires a data object (iddata
) as an input.
If you have the aforementioned toolbox, you can create a data object as in the example for retrend
, then add a trend similarly to what you already tried.
To my understanding, adding a delay is trickier, because you need to maintain the same vector length. You can pad your vectors with some dummy values (such as NaN
) in the correct direction.
Applied to your case we get:
function q45688607
%% Generate data:
t = (0 : 1 : 50).'; % Time Samples
f = 45; % Input Signal Frequency
Fs = 440; % Sampling Frequency
y = sin(2*pi*f/Fs*t);
d_data = iddata(y, t, 1/Fs);
%% Add offset:
T = getTrend(d_data);
% <detrend data if needed>
T.InputOffset = 5;
T.OutputOffset = 5;
afterOffset = retrend(d_data,T);
%% Add delay:
delaySamples = 8; % Must be a non-negative value
afterDelay = iddata([NaN(delaySamples,1); d_data.OutputData],...
[d_data.InputData; NaN(delaySamples,1)], 1/Fs);
%% Plot:
figure(); plot(d_data,afterOffset, afterDelay);
Yielding: