# csdms-contrib/slepian_alpha

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 function [Cp,Sp]=rotcof(C,S,angl) % [Cp,Sp]=ROTCOF(C,S,angl) % % Rotates real spherical harmonic coefficients over some angle % using essentially DT (C.245): multiplication by exp(im*angle). % % INPUT: % % C Cosine coefficients, as in LMCOSI(:,3), must start at 0 % S Since coefficients, as in LMCOSI(:,4), must start at 0 % angl Angle [radians] % % OUTPUT: % % Cp Cosine coefficients of rotated field % Sp Sine coefficients of rotated field % % SEE ALSO: ROTTP, PLM2ROT % % Last modified by fjsimons-at-alum.mit.edu, 07/19/2010 % Figure out maximum spherical harmonic degree L=addmup(length(C),'r'); % Initialize Cp=C; Sp=S; % Calculate exponential cangl=cos([0:L]*angl)'; sangl=sin([0:L]*angl)'; % warning('Changes. Updates consistent with ROTTP') for l=0:L % Extract coefficients [Cl,b,e]=shcos(C,l); Sl=shsin(S,l); % Rotate and collect - sign flipped 03/11/2010 Cp(b:e,1)=Cl.*cangl(1:l+1)+Sl.*sangl(1:l+1); Sp(b:e,1)=Sl.*cangl(1:l+1)-Cl.*sangl(1:l+1); end