Putting Mathematical Symbols and Subscripts Mixed With Regular Letters

Putting mathematical symbols and subscripts mixed with regular letters

Something like this :

g <- ggplot(data=data.frame(x=0,y=0))+geom_point(aes(x=x,y=y))
g+ xlab( expression(paste("Value is ", sigma,",", R^{2},'=0.6')))

EDIT

Another option is to use annotate with parse=T:

g+ annotate('text', x = 0, y = 0, 
        label = "Value~is~sigma~R^{2}==0.6 ",parse = TRUE,size=20) 

EDIT

The paste solution may be useful if the constant 0.6 is computed during plotting.

r2.value <- 0.90
g+ xlab( expression(paste("Value is ", sigma,",", R^{2},'=',r2.value)))

Putting mathematical symbols and subscripts mixed with regular letters

Something like this :

g <- ggplot(data=data.frame(x=0,y=0))+geom_point(aes(x=x,y=y))
g+ xlab( expression(paste("Value is ", sigma,",", R^{2},'=0.6')))

EDIT

Another option is to use annotate with parse=T:

g+ annotate('text', x = 0, y = 0, 
        label = "Value~is~sigma~R^{2}==0.6 ",parse = TRUE,size=20) 

EDIT

The paste solution may be useful if the constant 0.6 is computed during plotting.

r2.value <- 0.90
g+ xlab( expression(paste("Value is ", sigma,",", R^{2},'=',r2.value)))

Putting log symbols in ggplot2 text

Do you mean something like this?

ggplot(data.frame(x = seq(1:10), y = seq(1:10), label = "log[10]"), aes(x, y, label = label)) +
    geom_text(parse = T) +
    annotate("text", x = 1, y = 5, label = "2^log[2]", parse = T)

See this link for a list of mathematical expressions in plotmath.

How to add mathematical symbols in ggplot facet_wrap text?

add labeller = label_parsed to your facet_wrap function, format your unit as m^3, and replace spaces in your labels with ~

library(ggplot2)
dtf <- data.frame(year = rep(1961:2010,2),
                  consumption = cumsum(rnorm(100)),
                  item = rep(c("Tea~bags","Coffee~beans"),each=50),
                  unit = rep(c("T","m^3"),each=50))
ggplot(data=dtf)+
  geom_line(aes(x=year, y=consumption),size=1) +
  ylab(expression(paste("Consumption in T or ",m^3))) +
  scale_x_continuous(breaks = seq(1960,2010,10)) +
  theme_bw() + facet_wrap(item~unit, scales = "free_y",labeller = label_parsed)

ggplot2 - Text and Math in Annotation with Facet

try

geom_text(data=my.avg, aes(x=1.5, y=7, label=paste("Avg ==", mean, "*m^2/ha")), parse=TRUE)

Annotate different equations on facetted ggplot

Hopefully this satisfies both parts of the question. I'm also not great with putting together expressions.

For the first part, you can create a data frame of equation text from your data frame of intercepts and coefficients, and format it how you need. I set up the sprintf to match the number of decimal places you had, and to flag the coefficient's sign.

library(ggplot2)

# same preparation as in question
# renamed just to have standard column names
names(cars.coef) <- c("intercept", "mpg")

equation.text <- data.frame(
  cyl = unique(cars.pred$cyl),
  label = sprintf("y == %1.2f %+1.2f*x^{1}", cars.coef$intercept, cars.coef$mpg,
  stringsAsFactors = F)
)

The label column looks like this:

"y == 4.69 -0.09*x^{1}" "y == 6.42 -0.17*x^{1}" "y == 6.91 -0.19*x^{1}"

For the second part, you can just set parse = T in your geom_text, similar to the argument available in annotate.

ggplot(data = mtcars, mapping = aes(x = mpg, y = wt)) +
  geom_point() +
  geom_line(data = cars.pred, mapping = aes(x = mpg, y = wt)) +
  geom_text(data = equation.text, mapping = aes(x = 20, y = 5, label = label), parse = T) +
  facet_wrap(.~ cyl)

Notes on sprintf: % marks off where the formatting starts. I'm using + as the flag to include signs (plus or minus) to show the coefficient being either added or subtracted. 1.2f means including 1 place before the decimal point and 2 after; this can be adjusted as needed, but worked to display numbers e.g. 4.69. Arguments are passed to the format string in order as they're passed to sprintf.

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