Can the HP15C interpolate?



#4

I still have my trusty old HP15C, although I can't find the manual any longer. I'd like to use it in the field for doing photography calcs. I have graphs of exposure time vs. adjusted exposure time for pinhole cameras. I'd like to enter a series of X,Y data points from those graphs and ask the 15C do an interpolation (i.e. expected value) of a value of Y for a known value of X. Does anybody know if the 15C can be programmed for this type of operation and, if so, whether my best bet for doing learning the trick is to spring for the manuals on CD? Thanks.


#5

Yes, irt can, by doing a linear regression.

First, clear your stat reg (f <GSB>
Key in your Y,X values by doing Y1 <ENTER> Y2 <ENTER>
Then key f <L.R.>
A linear regression calculates a straight line that best fits with your series, equation Y=aX + b
you get 2 values : in X register is the b value stored, and in Y register the a value.

So all you have to do is with your new X value multiply it with your Y register value and add the X register value.

Should you wish to get other kind of regression, the following formulas are appliccable :

Power regression (Dx/x = C; Dy/y = C) : y = ab^x
Exp. regression : (Dx=C, Dy/y=c) : y : kax^b

just write down all X & Y values, calculate Dx, Dy, and Dx/x, Dy/y, and check what best fits. Then with 2 samples (preferably the most far of each other) calculate the 2 variables system of equation. Remeber your logs formulas :
loag a/b = log a-log b
loag ab : log a+log b
loag a^b = loag a . log b

Good luck

#6

yes, it can. in fact there is a built-in function on the bottom row of keys, y^, r (the linear estimation key). which operates on the data stored in the statistics registers.

providing your curves can be linearized with respect to the coefficients, probably you would like to calculate these coefficients once, and then create a program to use them. that way the statistics registers can be used for other purposes.

alternatively, the 15C manual describes an interpolation technique using tabulated values which involves entering the bracketing table values and calculating the intermediate one of interest. this served me well in my thermodynamics courses, but may not be too handy for your field work.

finally, i have a pretty nice one page summary of straight-line functions of certain equations. i'd be glad to mail you a copy if your interested.


Possibly Related Threads...
Thread Author Replies Views Last Post
  1984 HP15C rattles Footloose (Illinois) 4 911 10-15-2013, 09:43 PM
Last Post: BobVA
  HP15c continued fraction for Ln(Gamma) Tom Grydeland 0 508 09-30-2013, 05:48 AM
Last Post: Tom Grydeland
  HP15c LE emulator with unlimited number of activations Nick_S 23 2,914 01-24-2013, 03:59 PM
Last Post: Victor Quiros
  battery test for the HP15c Limited Edition Guido (Canada) 3 796 01-03-2013, 08:17 AM
Last Post: Jeff O.
  uRCL* on HP15C Csaba Tizedes (Hungary) 2 654 12-29-2012, 06:09 PM
Last Post: Luiz C. Vieira (Brazil)
  HP15C strange complex number behavior Mike W 5 974 09-11-2012, 04:36 PM
Last Post: Mike W
  HP15C Paul Averis ( Australia ) 1 551 06-18-2012, 03:33 AM
Last Post: Alexander Oestert
  HP15c LE - highest serial number over 23.000 Jose Gonzalez Divasson 1 574 05-16-2012, 03:19 AM
Last Post: Torsten
  HP15C LE Price Lowered by HP Namir 23 2,504 02-05-2012, 05:34 PM
Last Post: Andreas Grund
  HP15C LE Pause Operation not as expected Russell Dobson 13 1,593 02-03-2012, 05:43 PM
Last Post: Marcus von Cube, Germany

Forum Jump: