I'm studying computer science and rarely come in contact with physics. However, as part of one assignment, I had to approximate a function based on the following measured data.
(the quality is kind of low - the graph is totally discrete)
$x$-axis is voltage in volts, $y$-axis current in amperes.
Now I have approximated the function that would fit this data, let's call it $f(x)$.
Now I have to calculate differential resistance in 0.4V and 0.48V using this function. If I'm not wrong and my internet research skills are not embarassing, I should make the derivative of f(x) - let's call it f(x)' and simply calculate the value of f(0.4)' and f(0.48)', which would give me the respective differential resistances.
Am I wrong?