How do I calculate a derivative in excel when having x and y ...

[Jones]

I have two columns in Excel, one column being x values and the other being y values. How can I calculate the derivative and second derivative based on this information? Ultimately, I am looking to find the point on my graph at which the line is increasing and a decreasing rate.

[Joesy]

How far apart are your x values?  You can approximate the derivative by using the limit definition (i.e. (f(x+h) - f(x))/h as h goes to 0), which is basically the slope formula for a really small delta-x.  So say you have x's in column A and y's in column B.  Make a 3rd column for the first derivative and set the first value to be =(B2-B1)/(A2-A1) and drag that all the way down.  Then make a fourth column for the second derivative and use the formula (C2-C1)/(A2-A1), and drag that down.

Again this only works if your x values are close together!  The closer they are, the better.