# How to read scientific notation output (numbers that include “e”)? [duplicate]

After running the lm regression model using R, sometime one is bound to get very small P values or values in the covariance matrix. Something of the sort: -1.861246e-04 for example in a covariance matrix. My question is how do you read this? how could I perform calculations on it manually? I needed to multiply this covariance matrix out with a vector but since I do not know how to manipulate those numbers, I am lost.

• @Gordon Smyth Did O.P. really get : -1.861246e-04 for p-value? That is a negative number for p-value. Is that possible? – Mark L. Stone Dec 19 '17 at 22:28
• minus one point eight six times ten to the [power of] minus four – Henry Dec 20 '17 at 10:29

The "e" is a symbol for base-10 scientific notation. The "e" stands for $\times 10^{\rm exponent}$. So -1.861246e-04 means $-1.861246 \times 10^{-4}$. In fixed-point notation that would be -0.0001861246.
To not be completely OT I will just add that working with scientific notation to me looks a bit clunky(especially if you are publishing the results). To supress the notation in R use the command options(scipen=alpha) where alpha is the maximum number of digits for the result to be still expressed in fixed notation.