Re : Trendline equation from line

[Englund]

I'm having more a mathematical problem than just Labview related issue. In fact it can be regarded as both.
I want to predict results of a temperature rise as a logaritmic function.

I can do it in Excel and there i get an formula that i can calculate future values. The good with excel is that i can write the graph beoynd my measuring point.
I want to do the same in LV 8.2 to write the graph beoynd my measuring points.
Is this even possible to do or am i just waiting for a miracle to happen.

Regards,
Nicklas

[chilly_charly]

Since you have the equation and its parameters values, why don't you simply calculate new points to add, possibly using a different color to the previous ones ?

[Englund]

Because the values that i have is for 1 specific test. The equation changes when the values change. The base equation is y = A ln(x) +B that i know, but how to calculate the A and B so that they progress according to new values. It can be quite basic math, but at the moment i can't figure it out.

[chilly_charly]

You should have read the online Help ! 😉

Logarithm Fit Details
This VI fits data to a logarithmic function of the general form described by the following equation:

f = a ln(b.X) (= a ln (b) + a ln (X)

where x is the input sequence X, a is the amplitude, and b is the scale. This VI finds a and b that best fit the observations (X, Y).

a correspond to your A parameter, and a ln (b) is equal B)

You should use the a and b values returned by the Logarithm fit vi and calculate new Y values from an additionnal set of X vals.

Message Edité par chilly charly le 10-31-2007 02:54 PM

[Englund]

Thanks. I usually use only the local help or the forums. Thank you of that.