How to create Trignometric function lookup table

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Life is Wonderful 2021-4-15

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https://ww2.mathworks.cn/matlabcentral/answers/803176-how-to-create-trignometric-function-lookup-table

编辑： Life is Wonderful 2021-4-20

I need help to create a lookup table for twiddle factor generated by trignometric cosine and sine function ?

Thanks

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Life is Wonderful 2021-4-16

编辑：Life is Wonderful 2021-4-19

在 MATLAB Online 中打开

Thank you !

I was looking something like below code .

Can you pls add further to improve say 1/4 quater radian lookup table and calculate all angles / radians ?
What is best and efficient way for generating the lookup to get twiddle factor real and imaginary points ?
How fft and ifft calculation can be improved here in case I use cordic sine and cosine lookup table ?
cordiccosine and cordicsine Lookup table for N point FFT length ( say 1024,2048 upto 8192) ?

% Angle_rad = [-2*pi:1:2*pi];
close all;
clearvars;clc;
Angle_th = [0:1:360]; % 
lookup_table = cos(Angle_th*2*pi/360); % replace cos with
%  Replace current code here with pseudo
%  What is the size of lookup table ? FFT length -1 , N = 1024, N*m-1 ( m
%  =2,3,4 etc )
%  cdcCosineTh = cordiccos(th_Rad_fix = [-2*pi :steps: 2*pi]);
%  cdcsinTh    = cordicsin(th_Rad_fix = [-2*pi :steps: 2*pi]);
%  lookup_table[sizeof(FFT_Index)] = cordiccos(th_Rad_fix = [-2*pi :steps: 2*pi]) + -j*cordicsin(th_Rad_fix = [-2*pi :steps: 2*pi]);
%  Which Radix 2/4/8/16/64/128/256 for odd and even is suggested and why ?
%  How real and imaginary lookup table looks like
%  Input real_lookup_cordiccos(angles[0:360])
%  Input imag_lookup_cordicsin(angles[0:360])
%  Accuracy ,performat and speed are determined by total harmonic
%  distortion in -dBc i.e. SNR = rms( cordiccos & cordicsin -
%  lookup_table_real & lookup_table_imag)
%  It should work for iFFT and FFT implementation (reconstruct) without dC
%  and capture fundamental and all harmonics for 2 octave onwards
% clf;
figure;
subplot(3,2,1);
plot(1:size(Angle_th,2),cos(Angle_th*2*pi/360),'g--','Linewidth', 1.5); hold on; grid on;
xlabel('\theta');
h1.XLim = [0, 2*pi];
h1.XTick =[0:22.5:360];
h1.XTickLabel = {'0', '45', '90','135' , '180' ,  '225' ,  '270' ,  '315' ,  '360'};
h1.YTick = -1:0.5:1;
h1.YTickLabel = {'-1.0','-0.5','0','0.5','1.0'};
title('Trignometric-Cosine-Lookup-table');
subplot(3,2,2);
plot(1:size(Angle_th,2),sin(Angle_th*2*pi/360),'r--','Linewidth', 1.5); hold on; grid on;
xlabel('\theta');
h1.XLim = [0, 2*pi];
h1.XTick =[0:22.5:360];
h1.XTickLabel = {'0', '45', '90','135' , '180' ,  '225' ,  '270' ,  '315' ,  '360'};
h1.YTick = -1:0.5:1;
h1.YTickLabel = {'-1.0','-0.5','0','0.5','1.0'};
title('Trignometric-sine-Lookup-table');
subplot(3,2,3);
radian = (pi/180)*Angle_th;
plot(Angle_th,radian,'r--'); hold on; grid on;
xlabel('\theta');ylabel('Radian');
subplot(3,2,4);
radian = (pi/180)*Angle_th;
plot(Angle_th,cos(radian),'r--'); hold on; grid on;
xlabel('\theta');ylabel('ARC');
subplot(3,2,5);
degree = (180/pi)*radian;
plot(radian,(degree),'b--'); hold on; grid on;
h1.YLim = [0, 360];
h1.YTick =[0:22.5:360];
h1.YTickLabel = {'0', '45', '90','135' , '180' ,  '225' ,  '270' ,  '315' ,  '360'};
ylabel('\theta');xlabel('Radian');
subplot(3,2,6);
degree = (180/pi)*radian;
plot(radian,cos(degree),'b--'); hold on; grid on;
ylabel('\theta');xlabel('Arc');

Walter Roberson 2021-4-19

You asked for references about twiddle factor computation; I linked to a reference about twiddle factor computation.

If you had asked for a MATLAB implementation then I probably would not have posted any links. I do not have source code for that purpose, and I do not have time to research the topic and write the code.

https://www.eit.lth.se/sprapport.php?uid=554

https://www.researchgate.net/publication/271548634_A_new_method_to_generate_twiddle_factor_using_CORDIC_based_radix-4_FFT_butterfly

https://www.eejournal.ktu.lt/index.php/elt/article/view/1422/2445

Life is Wonderful 2021-4-20

编辑：Life is Wonderful 2021-4-20

No worries @Walter Roberson. Indeed it's super direction you have shared across. A big thank you .

I have some insight now . Folks have worked on this topic and there are advantage of using cordic algorithm for twiddle factor on DSP. May be MathWork documentation is poor and they should come up

With this I can write equation on a paper and start designing the code.

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