How to add a noise in my Input graph?

I have a input signal and i want to add noise to it with zero mean, variance of deviation = 1, sampling time is 600 and maxi deviation (%) is 15. Kindly help?

Answer 1

[hosein Javan]

this code gives a zero mean noise with a sampling rate equal to your signal. just calculate it's amplitude by knowing variance.

t = linspace(0,2*pi,100);
x = sin(t);
an = 0.2; % noise amplitude
noise = an*(rand(size(x))-0.5);
plot(t,x,'r','linewidth',1)
hold on
plot(t, x+noise)

[Adam Danz]

The standard deviation from a uniform distribution bounded by [0,1] (ie, rand) is usually around 0.083. It will be lower in your example since the values are multiplied by 0.2. I think the OP wants a variance (and std) of 1 which can be done with the randn function.

[Maham Arooj]

Sir, I want to add noise in the signal that shown in figure by usnig the above mention values....

[hosein Javan]

Adam Danz. I see. thanks for the advice.

[hosein Javan]

I used a data like yours. you should be fine sir.

use "rand" for uniformly distribution

use "randn" for normal distribution as Adam Danz said.

t = 0:20;
x = zeros(size(t));
% base kW = 100;
x(12:21) = 100*[1 2 3 4 5 6 9 5 3 1];
an = 1; % noise factor
% noise = an*(rand(size(x))-0.5);
noise = 100*an*(randn(size(x)));
stairs(t,x,'r','linewidth',1)
hold on
stairs(t, x+noise)

[Maham Arooj]

Thank you Sir...

[hosein Javan]

you're welcome.

Answer 2

[Adam Danz]

noise = randn(size(signal))

will return an array of random values from a standard normal distribution with mean=0 and variance=1. The array will be the same size as your signal. However, the max value has a very low probability that it will be greater than ~6. Remember that with standard normal distributions, 99.9% of all values are within +/- 3 from the mean.