Integrating above and below x axis separately

3 次查看（过去 30 天）
LRW
LRW 2020-12-23
评论： Image Analyst 2020-12-23
I have 90 trials of walking data that vary in duration, but the longest lasting 93 timestamps (so, I have a 93X90 matrix named Powers). Below is a plot of one trial, where the x axis is time and the y axis is Joint Power:
I am wanting to integrate the curve below and above the x axis separately so that I have the total positive and negative work. I have tried using if end statements and the trapz function but that didnt seem to work and I'm not sure why.
if Powers > 0
PosWork = trapz(Powers,1)
end
if Powers < 0
NegWork = trapz(Powers, 1)
end
How would I integrate a curve below and above the x axis separately for every column of my matrix? Any help is appreciated. Thank you in advance.

请先登录，再回答此问题。

采纳的回答

Star Strider
Star Strider 2020-12-23
With no if blocks:
t = linspace(0, 10); % Independent Variable
Powers = sin(2*pi*t) + randn(size(t))*0.1; % Signal (With Some Noise)
Poswork = trapz(t, Powers .* (Powers > 0)); % With Independent Variable (More Accurate)
Negwork = trapz(t, Powers .* (Powers < 0)); % With Independent Variable (More Accurate)
Poswork = trapz(Powers(:) .* (Powers(:) > 0), 1); % With Point Spacing, Forcing Column Vector
Negwork = trapz(Powers(:) .* (Powers(:) < 0), 1); % With Point Spacing, Forcing Column Vector
.

更多回答（1 个）

Image Analyst
Image Analyst 2020-12-23
Try
if Powers > 0
p2 = Powers
p2(p2 <= 0) = 0; % Zero out negative going values.
PosWork = trapz(p2, 1)
end
if Powers < 0
p2 = Powers
p2(p2 >= 0) = 0; % Zero out positive going values.
NegWork = trapz(p2, 1)
end
  5 个评论
显示 3更早的评论
Image Analyst
Image Analyst 2020-12-23
Looks like you no longer need help since you accepted Star's answer.
Image Analyst
Image Analyst 2020-12-23
OK, I did it because it doesn't look like Star's solution reads in your data and does it over all your columns like you wanted. Try this:
clc; % Clear the command window.
clear all;
close all;
workspace; % Make sure the workspace panel is showing.
format short g;
format compact;
fontSize = 15;
fprintf('Beginning to run %s.m ...\n', mfilename);
Powers = csvread('Powers.csv')
x = Powers(:, 1);
subplot(1, 2, 1);
[rows, columns] = size(Powers);
for col = 2 : columns
thisY = Powers(:, col);
thisX = x;
% Remove any nans
nanInidexes = isnan(thisY);
thisY(nanInidexes) = [];
thisX(nanInidexes) = [];
p2 = thisY; % Initialize
% Plot it.
plot(thisX, thisY, '-');
grid on;
hold on;
p2(thisY <= 0) = 0; % Zero out negative going values.
PosWork(col-1) = trapz(p2, 1)
p2 = thisY; % Re-initialize.
p2(thisY >= 0) = 0; % Zero out positive going values.
NegWork(col-1) = trapz(p2, 1)
end
title('Individual Data', 'fontSize', fontSize);
subplot(1, 2, 2);
plot(PosWork, 'b-', 'LineWidth', 2);
hold on;
plot(NegWork, 'b-', 'LineWidth', 2);
grid on;
xlabel('x', 'fontSize', fontSize);
ylabel('Work', 'fontSize', fontSize);
legend('Positive Work', 'Negative Work');
title('Work', 'fontSize', fontSize);
g = gcf;
g.WindowState = 'maximized';
fprintf('Done running %s.m ...\n', mfilename);

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Numerical Integration and Differentiation 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by