How to tabulate?

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prem kumar
prem kumar le 29 Jan 2022
Réponse apportée : Voss le 29 Jan 2022
hello friends i want to ask a question regarding tabulation of number of days and sdelta without the statistic toolbox.
dn=1:1:365;
x=(360/365*(dn+284));
sdelta=23.45*(sind(x)*pi/180);
Tabulate sdelta for dn = 15, 45, 75, 105, 135, 165, 195, 225, 255, 285, 315, 345.
for normal tabulation for dn and sdelta is easy i believe but how about when the number of days is like this?i did thought about interpolation but i think it would not be that complicated and must have a simpler way to solve it ..can anyone give me a hint or guide me?.Thank you friends

Réponse acceptée

KSSV
KSSV le 29 Jan 2022
You can use interp1.
dn=1:1:365;
x=(360/365*(dn+284));
sdelta=23.45*(sind(x)*pi/180);
dni = [15, 45, 75, 105, 135, 165, 195, 225, 255, 285, 315, 345] ;
sdeltai = interp1(dn,x,dni);
  1 commentaire
prem kumar
prem kumar le 29 Jan 2022
owh ok noted thank you friend.

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Voss
Voss le 29 Jan 2022
You do not need to interpolate because the dn values you want the sdelta for are all already in the vector of all dn values (i.e., 1:1:365 contains 15, 45, 75, ...); you merely need to take those indices of sdelta:
dn=1:1:365;
x=(360/365*(dn+284));
sdelta=23.45*(sind(x)*pi/180);
dni = [15, 45, 75, 105, 135, 165, 195, 225, 255, 285, 315, 345];
sdeltai = sdelta(dni) % get elements of sdelta at indices dni
sdeltai = 1×12
-0.3712 -0.2377 -0.0422 0.1643 0.3280 0.4061 0.3783 0.2518 0.0597 -0.1480 -0.3171 -0.4035
isequal(sdeltai,interp1(dn,sdelta,dni)) % same as "interpolating"
ans = logical
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