| 'vectorizing functions' [message #52524] |
Tue, 06 February 2007 03:58 |
leatherback
Messages: 15
Registered: November 2005
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Junior Member |
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Dear All,
I am working on a script to convert a whole series of x-y coordinates
into path-descriptions:
- Distance between two points
- Angle compared to <0,1> vector
- Angle between consecutive steps
I -think- I have a function which calculates the angle between 2
vectors. However, as I have long lists of points (At the moment some 3
million, and growing with 100/hr) I would like to do this based on
blocks of data, and use the IDL ability to do array-calculations.. I
have written a buffer-reader for my data, which will allow me to read
chunks of data from a file. I would like to process each chunk in one
go, instead of one point at a time. Could somebody perhaps assist me
in converting the functions I have written, and accept points [x,y],
to functions that will operate on arrays [[x], [y]] of points?
Thanks!
The functions:
function calculate_length, vector
length = sqrt(vector[0]^2 + vector[1]^2)
return, length
end
;--------------------
function calculate_angle, vector1, vector2
; Length of the two vectors
length1 = calculate_length(vector1)
length2 = calculate_length(vector2)
;==> Before running check whether Cos_theta=0 is valid in all cases.
Prob. not! <==
if ((length1 EQ 0) or (length2 EQ 0)) THEN begin
Cos_theta = 0
endif else begin
Cos_theta = (TRANSPOSE(vector1) # vector2) / (length1 * length2)
endelse
Theta = ACOS(Cos_theta) * (180 / !pi)
return, Theta
end
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