Hi, I am a student carrying out work with assessing weather data and have 4000+rows of data that need formula applied to the. The formula that needs to be applied is dependent on the magnitude of the values for x and y. i.e for: x> apply arctan y/x y>=0,x<0 appply arctan y/x +pi y<0,x<0 apply arctan y/x -pi y>0,x=0 apply +pi/2 y<0,x=0 apply -pi/2 y=0,x=0 apply undefined is there any way of doing this that does't require going through them one by one? Any help greatly appreciated. Regards, Matthew
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