How to tabulate?

Question

prem kumar 2022-1-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1638545-how-to-tabulate

回答： Voss 2022-1-29

采纳的回答： KSSV

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

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Answer 1

KSSV 2022-1-29

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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);

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prem kumar 2022-1-29

owh ok noted thank you friend.

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Answer 2

Voss 2022-1-29

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https://ww2.mathworks.cn/matlabcentral/answers/1638545-how-to-tabulate#answer_884575

在 MATLAB Online 中打开

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
   1