as.mpoly: Convert an object to an mpoly

In dkahle/mpoly: Symbolic Computation and More with Multivariate Polynomials

Convert an object to an mpoly

Description

mpoly is the most basic function used to create objects of class mpoly.

Usage

as.mpoly(x, ...)

Arguments

x	an object
...	additional arguments to pass to methods

Value

the object formated as a mpoly object.

Author(s)

David Kahle [e-mail]

See Also

mp()

Examples

library(ggplot2); theme_set(theme_classic())
library(dplyr)

n <- 101
s <- seq(-5, 5, length.out = n)



# one dimensional case

df <- data.frame(x = seq(-5, 5, length.out = n)) %>%
  mutate(y = -x^2 + 2*x - 3 + rnorm(n, 0, 2))

(mod <- lm(y ~ x + I(x^2), data = df))
(p <- as.mpoly(mod))
qplot(x, y, data = df) +
  stat_function(fun = as.function(p), colour = "red", size = 1)

(mod <- lm(y ~ poly(x, 2, raw = TRUE), data = df))
(p <- as.mpoly(mod))
qplot(x, y, data = df) +
  stat_function(fun = as.function(p), colour = "red", size = 1)

(mod <- lm(y ~ poly(x, 1, raw = TRUE), data = df))
(p <- as.mpoly(mod))
qplot(x, y, data = df) +
  stat_function(fun = as.function(p), colour = "red", size = 1)



# two dimensional case with ggplot2

df <- expand.grid(x = s, y = s) %>%
  mutate(z = x^2 - y^2 + 3*x*y + rnorm(n^2, 0, 3))
qplot(x, y, data = df, geom = "raster", fill = z)

(mod <- lm(z ~ x + y + I(x^2) + I(y^2) + I(x*y), data = df))
(mod <- lm(z ~ poly(x, y, degree = 2, raw = TRUE), data = df))
(p <- as.mpoly(mod))
df$fit <- apply(df[,c("x","y")], 1, as.function(p))

qplot(x, y, data = df, geom = "raster", fill = fit)

qplot(x, y, data = df, geom = "raster", fill = z - fit) # residuals

dkahle/mpoly documentation built on July 27, 2023, 11:44 p.m.