Estimate first or second derivatives for dy/dx.

Uses central differencing where possible.

Usage

deriv(x, y, ord = 1, method = "direct", ends = "forwardback")

Arguments

x

x variable. Does not need to be evenly spaced.

y

y variable.

ord

Order of the derivative (1 or 2).

method

Method for taking second derivatives. Either

• 'direct' (default) Uses a direct formula, based on a central difference of forward and backward differences, from https://mathformeremortals.wordpress.com/2013/01/12/a-numerical-second-derivative-from-three-points/

• 'repeat' Repeat two first derivatives.

ends

('forwardback', 'NA', or 'drop') How to handle the endpoints where central differencing is not possible. 'forwardback' (default) uses forward differencing at the first point and backward differencing at the last. 'NA' sets endpoints to NA. 'drop' removes the endpoints.

Value

Derivative of y relative to x.