# How to figure out an equation from a plot?

I am trying to figure out the equations y=f(x) of the red dashed lines in this log-linear graph where the x values were plotted on a logarithmic scale while the y values were kept linear.

I tried to figure it out from the table below which revealed a geometric serie starting from the third X value (i.e x=25) but I am not sure how i can utilize mathematica to resolve this issue.

.

Using the incidence data from your table:

loglinIncidence = {Log10[#1], #2} & @@@
Transpose@{{5, 10, 25, 50, 100, 200}, {1, 1.11, 1.27, 1.4, 1.55, 1.71}};
model = LinearModelFit[loglinIncidence, {1, x}, x]

Plot[
model[x], {x, Log10[5], Log10[200]},
Epilog -> {Red, PointSize[0.02], Point[transformedData]}
]


One should then be able to do the same with the mortality data set to get your second equation.

• @MarcoB.Thank you so much! Nov 23 '16 at 19:41
• @PureFunction Glad to help! Nov 23 '16 at 21:35