how to find the amplitude?

Hello

Im writing a code for calculating blood pressure. My problem is i don't know how to solve this. I think it will be a lot easier if i knew how to "rotate" my graph(there is a picture attached). My data is number 1 in the picture. I would like to have it as no. 2.

I hope one of your guys can help me.

In advance thanks :)

Answer 1

[Image Analyst]

How about you fit a line or quadratic to your data with polyfit(). Then subtract it from the signal to get the residuals. Then subtract the min of the residuals and plot it.

x = 1 : length(y);
polynomialOrder = 1; % for line, or 2 for quadratic.
coefficients = polyfit(x, y, polynomialOrder);
% Get fitted line
fittedLine = polyval(coefficients, x);
% Get delta y between fitted line and actual data.
r = y - fittedLine;
% That r will have positive and negative elements.
% Raise the curve by subtracting the min
% so that there will be only positive values.
new_y = r - min(r);
plot(x, new_y, 'r-', 'LineWidth', 2);
grid on;
fontSize = 20; % whatever size you want.
xlabel('Time', 'FontSize', fontSize);
ylabel('Blood Pressure', 'FontSize', fontSize);