Resampling Data using Interp1

Question

Lucianne Morin 2020-6-29

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/556900-resampling-data-using-interp1

评论： Star Strider 2020-7-1

Hello!

This may be a fairly obvious answer, but I'm trying to resample some data down to 100 Hz using interp1. I load my data, and then extract the first column (which is the time series) to use in my for loop. However, I get the error "Interpolation requires at least two sample points in each dimension." I tried adjusting the code to call for a(i+1) to see if maybe I needed to start later, but I got the same error. The data itself is part of my thesis so I'm not sure if I can attach it, but I've copy and pasted my code below.

Thank you in advance for any help!

load('BNI_processed.mat')
a = Force_arr;
time_matrix =(a(1:end,1)).';
for i = 1:length(time_matrix)-2
aa = length(time_matrix(i):time_matrix(i+1));
p = 61;
Force(:,i)=interp1(a(i,2),1:aa/p:aa, 'spline');
end

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Image Analyst 2020-6-30

Youi forgot to attach the mat file. We'll check back tomorrow.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Star Strider 2020-6-30

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/556900-resampling-data-using-interp1#answer_458821

You are doing signal processing. For that, use the resample function. It will do the interpolation, and will also use an anti-aliasing filter to remove unwanted artifacts. I am not certain what your signal is or what you want to do with it, so I cannot provide a link to the most appropriate section of the resample documentation for that.

2 个评论
显示无隐藏无

Lucianne Morin 2020-7-1

BNI_Data1.m

The reason why I'm not using the resample function is because my data is derived from the activation of pressure sensors, so the sampling frequency isn't consistant across the time series (it's 128.5935...). I spent some time trying to set the two integers to get it, but I need to resample to 100 Hz exactly and it wasn't working out. I'm attaching my code if that helps, I did find a work around for the interp1 but there is aliasing in the data right now.

Thanks for your help.

Star Strider 2020-7-1

在 MATLAB Online 中打开

I was hoping for ‘BNI_processed.mat’. Lacking it, the resample function can do exactly what you wantpreviously, since I have done this previously.

From the documentation (there is no specific link to this line):

y = resample(x,tx,fs) uses a polyphase antialiasing filter to resample the signal at the uniform sample rate specified in fs.

Referring to your code, this would probably be:

[force_array, p_new] = resample(a(:,2:end), p, 100);
[shoe_array, q_new] = resample(b(:,2:end), q, 100);

I cannot determine for certain that will work because I do not have ‘BNI_processed.mat’ to work with and check. I am going only by your interp1 calls.

Without ‘BNI_processed.mat’, my only option is to post this as UNTESTED CODE. It should do what you want.

.

请先登录，再进行评论。

Answer 2

Walter Roberson 2020-7-1

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/556900-resampling-data-using-interp1#answer_459370

编辑：Walter Roberson 2020-7-1

在 MATLAB Online 中打开

load('BNI_processed.mat')
input_forces = Force_arr(:,2);
time_matrix = Force_arr(:,1);
Fs = 100;
last_time = ceil(time_matrix(end) / Fs) * Fs;   %round UP
time_to_interp = 0 : 1/Fs : last_time;
Force = [time_to_interp; interp1(time_matrix, input_forces, time_to_interp)] .;