Problems using trapz() - dimension issue

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Bran
Bran 2014-1-13
评论： Matt J 2014-1-16
clc
clear all;
Az=load('TEXT PILOT CC LANKLE_converted_1.txt');
Az1=Az(:,1);%looking at the velocity in x first
A = length(Az1);
time = (length(Az1)/40); % the amount of time the device was switched on for
t = 0:(1/40):time; % seperating time properly
Az2=(Az1*9.81);%converting the data into m/s^2
vz = trapz(t,Az2);
plot(vz)
I am trying to integrate discrete data from an accelerometer so that I can plot a graph for the velocity I have attempted this a number of ways including using trapz(). I use the code above but I get the following error,
??? Error using ==> trapz at 59
LENGTH(X) must equal the length of the first non-singleton dimension of Y.
Error in ==> test_velocityusingtrap2 at 10
vz = trapz(t,Az2);
any ideas would be great!

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采纳的回答

Matt J
Matt J 2014-1-13
t=linspace(0,time,length(Az2));
  2 个评论
Matt J
Matt J 2014-1-16
Bran's Comment relocated,
Hi there thank you so much this has resolved my dimensions problem however, the plot I get for velocity using trapz() isn't very meaningful is this code more useful
clc clear all;
Az=load('converted_1.txt');
Az1=Az(:,1);%looking at the velocity in x first A = length(Az1); time = (length(Az1)/40); % the amount of time the device was switched on for
t=linspace(0,time,A); % seperating time properly
Az2=(Az1*9.81);%converting the data into m/s^2
Az3 = padarray(Az2,[0 3],'post');
vz(length(Az1),:)=0; % setting out a vector containing zero's to then fill
i=1;
while (i<A)
vz(i)=((t(i+1)-t(i))*((Az3(i)+Az3(i+1))/2));
i=i+1;
end
Also I am confused about what I shoud be using for the inital conditions do I need to add vz(i) to my calcualtions as well, I thought I just need to add v(0) to each which I am assuming to be zero? plot(vz)
Matt J
Matt J 2014-1-16
Yes, it sounds like you would add v(0).

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