DM32 Curve Fit - Make It Tea

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====== DM32 Curve Fit ======

** CFIT Program from the Owner's Manual **

===== State File =====

The listing from the Owner's Manual has been entered into the calculator and saved as a State File

{{ :public:calculator:guides:cfit.d32 |}}


===== Use =====

The program provides the usual set of Curve Fitting for Straight Line, Exponential, Logarithmic and Power curves, automating the same techniques as the manual method for DM15 described here [[dm15l_curve_fit|]] .

There is no "best fit" algorithm, which means you need to decide in advance which of the 4 curve types to fit, before entering the data. If you choose a different curve you have to enter the data again.

==== Choose a Curve ====

Each curve type has a separate program label

  * <key>XEQ</key> <key>'S'</key> : Straight Line
  * <key>XEQ</key> <key>'E'</key> : Exponential
  * <key>XEQ</key> <key>'L'</key> : Logarithmic
  * <key>XEQ</key> <key>'P'</key> : Power

==== Enter Data ====


Data is entered the same way whichever of the 4 programs is chosen.

  * X-value <key>R/S</key> Y-value <key>R/S</key>
  * X-value <key>R/S</key> Y-value <key>R/S</key>
  * X-value <key>R/S</key> Y-value <key>R/S</key>
  * X-value <key>R/S</key> Y-value <key>R/S</key>

==== Run the Curve Fit ====

Once all the data is entered you run the fit using <key>XEQ</key> <key>'R'</key>

This gives the various paramaters

  * R-value (correlation coefficient) <key>R/S</key>
  * B-value <key>R/S</key>
  * M-value <key>R/S</key>
  * Prompt for an x-value to use to calculate ŷ - enter a number <key>R/S</key>
    * ŷ is shown for that x-value
  * Prompt now for a y-value to use to calculate an estimate of x <key>R/S</key>
    * x estimate is shown for that y-value
  * Prompt for a new x-value to use to calculate ŷ <key>R/S</key>
    * this goes on until you want to stop....
    * press <key>'C'</key> to quit

===== Curve equations =====

  * Straight Line '' y = B + Mx ''
  * Exponential '' y = Be<sup>Mx</sup> ''
  * Logarithmic '' y = B + M Ln(x) ''
  * Power '' y = Bx<sup>M</sup> ''

===== Examples =====

==== Logarithmic ====

|x|0.3|1|2|3|4|5|
|y|-1|2|3.8|5|5.6|6|

  * <key>XEQ</key> <key>'L'</key>
  * 0.3 <key>R/S</key> 1 <key>'+/-'</key> <key>R/S</key>
  * 1 <key>R/S</key> 2 <key>R/S</key>
  * 2 <key>R/S</key> 3.8 <key>R/S</key>
  * 3 <key>R/S</key> 5 <key>R/S</key>
  * 4 <key>R/S</key> 5.6 <key>R/S</key>
  * 5 <key>R/S</key> 6 <key>R/S</key>

Data is complete - run the fit

  * <key>XEQ</key> <key>'R'</key>
  * ''R=0.99932'' <key>R/S</key>
  * ''B=2.05210'' <key>R/S</key>
  * ''M=2.5359'' <key>R/S</key>
  * enter an x-value to calculate an estimate of y
    * 2.5 <key>R/S</key>
    * ''y? 4.37571''
  * enter a y-value to calculate an estimate of x
    * 0.8 <key>R/S</key>
    * ''X ? 0.61033''
  * finish <key>'C'</key>

The curve equation is '' y = 2.05210 + 2.5359Ln(x) ''



===== Further Information =====


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Page created  : 17/04/26 08:35 BST

Page updated : ~~LASTMOD~~

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