使用FFT方法插值1-D数据并可视化结果。

Generate some sample points in the interval $$[0,3\pi ]$$for the function $$f(x)={\sin }^2(x)\cos (x)$$。使用间隔间隔dxto ensure the data is evenly spaced. Plot the sample points.

dx = 3*pi/30; x = 0:dx:3*pi; f = sin(x).^2 .* cos(x); plot(x,f,'o')

使用FFT插值在200个查询点找到功能值。

N = 200; y = interpft(f,N);

Calculate the spacing of the interpolated data from the spacing of the sample points withdy = dx*长度（x）/n, whereNis the number of interpolation points. Truncate the data inyto match the sampling density ofx2。

dy = dx*长度（x）/n; x2 = 0:dy:3*pi; y = y(1:length(x2));

Plot the results.

hold上plot(x2,y,'.') title('FFT Interpolation of Periodic Function')

Generate three separate data sets of normally distributed random numbers. Assume the data is sampled at the positive integers,1:N。Store the data sets as rows in a matrix.

a = randn（3,20）;x = 1:20;

Interpolate the rows of the matrix at 500 query points each. Specifydim = 2so thatinterpftworks on the rows ofA。

N = 500; y = interpft(A,N,2);

Calculate the spacing interval of the interpolated datady。Truncate the data inyto match the sampling density ofx2。

dy = length(x)/N; x2 = 1:dy:20; y = y(:,1:length(x2));

Plot the results.

subplot(3,1,1) plot(x,A(1,:)','o'); hold上plot(x2,y(1,:)','--') title('Row 1') subplot(3,1,2) plot(x,A(2,:)','o'); hold上plot(x2,y(2,:)','--') title('Row 2'）子图（3,1,3）图（x，a（3，:)'，，，'o'); hold上plot(x2,y(3,:)','--') title('Row 3')