False result why applying interp1 function!

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inti 2014-7-18

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https://ww2.mathworks.cn/matlabcentral/answers/142358-false-result-why-applying-interp1-function

关闭： MATLAB Answer Bot 2021-8-20

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Hi to all,

I have data taken at non-regular intervals, and I'd like to interpolate the data to have values every 100ms.

if 
43:08.437 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
43:08.477 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
43:08.497 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
43:08.516 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
43:08.537 > ATT_HandleValueNotification: status=0 h=45 n=3 09 C7 17
43:08.577 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
end

My code is :

if s=data(:,3)+data(:,4)/1000; % convert to seconds+fractions
t = datenum(2014,07,18,data(:,1),data(:,2),s)*86400;
t = t - t(1);
sample = interp1(t,res(:,1:3), 0:0.01:t(end)); % i fixed a time to 100ms to obtain estimated data in this time 
 // end

Thanks in advance

end

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the cyclist 2014-7-18

编辑：the cyclist 2014-7-18

@inti,

By far the best thing you can do to help us solve your problem is to give us a small piece of functioning MATLAB code (including the part that defines the data) that illustrates the problem. Otherwise, we spend far too much time guessing.

inti 2014-7-18

在 MATLAB Online 中打开

Thanks for your reply.

I have irregular time series data: (time (h:m:s:ms), X-acceleration, Y-acceleration, Z-acceleration)in hexadecimal

Portion of my log file

if 17:43:08.437 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
17:43:08.477 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
17:43:08.497 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
17:43:08.516 > ATT_HandleValueNotification: status=0 h=45 n=3 07 C7 17
17:43:08.537 > ATT_HandleValueNotification: status=0 h=45 n=3 09 C7 17
end

The first column is for a Time and the three last columns are for acceleration's data (x,y,z).

My goal here is to interpolate irregular Time series to regular time series and i like to obtain acceleration's data every 0.01 seconds.

After converting acceleration's data from hexadecimal to acceleration's g , i obtain this table

if 0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,140625000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
end

And this a portion of a table sample after applying interp1 function :

if 
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
0,110866306584362  -0,890625000000000  0,359375000000000
0,125746056832695  -0,890625000000000  0,359375000000000
0,140624576267240  -0,890625000000000  0,359375000000000
0,132812426778048  -0,890625000000000  0,359375000000000
0,125000277288855  -0,890625000000000  0,359375000000000
0,117188127799663  -0,890625000000000  0,359375000000000
0,109375978310470  -0,890625000000000  0,359375000000000
0,109375000000000  -0,890625000000000  0,359375000000000
end
i think that i have a duplicate values