obtain 300 values from 840 values

Hello everybody,

I have one column S with 840 values. I would like to ultimately obtain 300 values because I would like to do a correlation analysis with another column containing 300 values. What would be the formula to use to do that? Could I do an average from several values, and how could I write that?

Thank you!

[Image Analyst]

WE don't know the formula. Just how are these 300 values to be arrived at? Taken randomly from the 840 values? Use the first 300? Take a moving average of some values? Use every other value? We have no idea, but surely you must have some idea as to how to generate these 300 values. Tell us.

[KALYAN ACHARJYA]

@Image Analyst sir Can apply interp1?? or Zero Padding?

[Anastasia]

Thank you. Actually, I would like for the signal with the 300 values to be as close as possible from the signal from the 840 values. Either I would use every third value but I would have 280 values in the end, so I thought, as you mentioned, generate a kind of moving average that would ultimately give me 280 values, but I do not know how to do that. Thank you for your help.

[KSSV]

Have a look on interp1.

Answer 1

[Image Analyst]

Anastasia, you still haven't specified what you want, so here is one guess. I just interpolate between all the points and uniformly sample the 300 points between the first point and the last point:

clc;  % Clear command window.
clear;  % Delete all variables.
close all;  % Close all figure windows except those created by imtool.
imtool close all;  % Close all figure windows created by imtool.
workspace;  % Make sure the workspace panel is showing.
fontSize = 15;

% Make 840 random values
numPoints = 840
period = 100;
x = 1 : numPoints;
v = 3 * cos(2 * pi * x / period) + rand(1, numPoints);
% Get 300 "x" values
xq = linspace(1, length(v), 300);
v300 = interp1(x, v, xq);

% Plot everything
subplot(3, 1, 1);
plot(x, v, 'b.-', 'LineWidth', 2, 'MarkerSize', 10);
grid on;
title('840 Points', 'FontSize', fontSize);

subplot(3, 1, 2);
plot(xq, v300, 'ro', 'LineWidth', 2, 'MarkerSize', 7);
grid on;
title('300 Points', 'FontSize', fontSize);
% Smooth the signal
vSmooth = conv(v, ones(1, 15), 'same');
% Get 300 "x" values
xq = linspace(1, length(v), 300);
vs300 = interp1(x, vSmooth, xq);
subplot(3, 1, 3);
plot(xq, vs300, 'ro', 'LineWidth', 2, 'MarkerSize', 7);
grid on;
title('300 Smoothed Points', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0.04, 1, 0.96]);