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MathGroup Archive 1995

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any better to apply a function to second column?

  • To: mathgroup at christensen.cybernetics.net
  • Subject: [mg507] any better to apply a function to second column?
  • From: Richard Q. Chen <chen at fractal.eng.yale.edu>
  • Date: Sun, 5 Mar 95 11:25:35 EST

Hi,
	I would like to know if there is a better way to
do the following.

	Suppose I have list of numbers in pairs:

a = {{x1,y1},{x2,y2},...,{xn,yn}}

I would like to apply to the sequence {y1,y2,...,yn} the function
f so that a new sequence

b = {{x1,f[y1]},{x2,f[y2]},...,{xn,f[yn]}}

is generated.

My current solution is

b = Transpose[{First /@ a,f[Last /@ a]}]

However, I suspect there should be a much more simpler way than this.

Does any body know a more straight forward way to do this?

Also, what if I have a matrix of 3 or more columns and I would apply
f to only the second column, say. What is a better way in this case?

Thanks for any info

Richard



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