interp1 returning NaN for values <1
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Hey all,
I have a function that I am using as part of another program, and it relies on interp1, however, my interp1 function is not returning a mix of NaNs and numbers. Here is my code:
function [T] = thrust(t);
thrust_time = xlsread('rocketdata.xlsx')
e = length(thrust_time)
time_reduced = thrust_time((1:e),2);
thrust_reduced = thrust_time((1:e),1);
A = interp1(time_reduced,thrust_reduced)
T = A(t)
end
where the XLS file has 2 columns of 153 rows. The first column is Thrust, and the second column is time. All values are positive, but the first ~25 and last ~25 thrust values are decimals less than 1 but greater than zero, which return NaN. All thrust values greater than 1 return actual numbers.
Can anyone please tell me what I am doing wrong? Thank you!
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Star Strider
2014-4-29
编辑：Star Strider
2014-4-29
1 个投票
I don’t know what the contents and ranges of time_reduced and thrust_reduced are. I suspect you may be asking interp1 to interpolate values not within the range of the data, but that’s only a guess. You will need to specify a third argument to interp1 if you want it to interpolate values for thrust_reduced at new times for time_reduced.
vq = interp1(v,xq) returns interpolated values and assumes a default set of sample point coordinates. The default points are the sequence of numbers from 1 to n, where n depends on the shape of v:
- When v is a vector, the default points are 1:length(v) .
- When v is an array, the default points are 1:size(v,1) .
Use this syntax when you are not concerned about the absolute distances between points.
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