can someone help me find the eqaution of this graph
it has to be in the formatt of
y=e
I have uploaded a corrected plot.Originally Posted by calem_123
Try to avoid using proprietary file formats like Excel and Word, Not everyone
has these on their machines. Try to stick to something like .JPG, .PNG
graphics files.
RonL
Nobody will be able to fine the equation of the graph.Originally Posted by calem_123
They will be able to find an equation which approximates the graph.
Now your statement about the required format of the equation is not
clear, I take it to mean that you want an equation in the form:
$\displaystyle
y=e^{f(x)}
$
for some function $\displaystyle f$ of $\displaystyle x$. Is that right?
RonL
Using the excell solver to fit an equation of the form:
$\displaystyle
y=K e^{a+bx+cx^2}}
$
to a selection of data points from this curve I get:
$\displaystyle
y=25e^{1.098-0.02429x+0.000256x^2}
$
but this is not as good a fit as I would like to see.
RonL
Oops, the $\displaystyle a$ term is redundant, this is equivalent to:Originally Posted by CaptainBlack
$\displaystyle
y=74.95e^{-0.02429x+0.000256x^2}
$
or absorbing the $\displaystyle K$ instead of the $\displaystyle a$ term:
$\displaystyle
y=e^{3.5343-0.02429x+0.000256x^2}
$
(The rational function approximation is better though)
RonL
Choose three points on the graph $\displaystyle (x_1,y_1),\ (x_2,y_2),\ (x_3,y_3)$, then you have a set of equations:Originally Posted by calem_123
$\displaystyle y_1=e^{a+bx_1+cx_1^2}$
$\displaystyle y_2=e^{a+bx_2+cx_2^2}$
$\displaystyle y_3=e^{a+bx_3+cx_3^2}$,
now take logs of these equations:
$\displaystyle \log(y_1)=a+bx_1+cx_1^2$
$\displaystyle \log(y_2)=a+bx_2+cx_2^2$
$\displaystyle \log(y_3)=a+bx_3+cx_3^2$.
This is a set of three linear simultaneous equations in variables $\displaystyle a,\ b,$ and $\displaystyle c$, which can be solved by the usual methods.
This method is not advised.
RonL