Convert String Back into Object in R

convert string back into object in r

I'm assuming you used base::dput() according to the following example (based on this answer):

# Generate some model over some data
data <- sample(1:100, 30)
df <- data.frame(x = data, y = 2 * data + 20)
model <- lm(y ~ x, df)

# Assuming this is what you did you have the model structure inside model.R
dput(model, control = c("quoteExpressions", "showAttributes"), file = "model.R")

# ----- This is where you are, I presume -----
# So you can copy the content of model.R here (attention to the single quotes)
mstr <- '...'

# Execute the content of mstr as a piece of code (loading the model)
model1 <- eval(parse(text = mstr))

# Parse the formulas
model1$terms <- terms.formula(model1$terms)

# ----- Test it -----
# New data
df1 <- data.frame(x = 101:110)

pred <- as.integer(predict(model, df1))
pred1 <- as.integer(predict(model1, df1))

identical(pred, pred1)
# [1] TRUE

model
# 
# Call:
# lm(formula = y ~ x, data = df)
# 
# Coefficients:
# (Intercept)            x  
#          20            2  
# 

model1
# 
# Call:
# lm(formula = y ~ x, data = df)
# 
# Coefficients:
# (Intercept)            x  
#          20            2  

# Check summary too (you'll see some minor differences)
# summary(model)
# summary(model1)

How to convert a string in a function into an object?

The trick is to use parse. For instance:

> x <- "A"
> eval(parse(text=paste("df$", x, sep = "")))
 [1]  1  2  3  4  5  6  7  8  9 10

See also this Q/A: Evaluate expression given as a string

Convert string to datatime object in r

As previous comments and answers suggested, the POSIXct (i.e., datetime) class in R always stores dates along with times. If you convert from a character object with just times to that class, today's date is added by default (if you want another date, you could do, for example, this: as.POSIXct(paste("2020-01-01", times), format = "%Y-%m-%d %H:%M")).

However, this should almost never be a problem since you can use format(times, format = "%H:%M") or for ggplot2 scale_x_datetime to get just the times back. For plotting, this would look something like this:

times <- c("00:30", "01:30", "02:30", "03:30", "04:30", "05:30", "06:30", "07:30", "08:30", "09:30", "10:30", "11:30", "12:30", "13:30", "14:30",
           "15:30", "16:30", "17:30", "18:30", "19:30", "20:30", "21:30", "22:30", "23:30")

library(tidyverse)
df <- tibble(
  time_chr = times,
  time = as.POSIXct(times, format = "%H:%M"),
  value = rnorm(length(times))
)
df
#> # A tibble: 24 x 3
#>    time_chr time                 value
#>    <chr>    <dttm>               <dbl>
#>  1 00:30    2020-03-12 00:30:00  0.352
#>  2 01:30    2020-03-12 01:30:00 -0.547
#>  3 02:30    2020-03-12 02:30:00 -0.574
#>  4 03:30    2020-03-12 03:30:00  0.843
#>  5 04:30    2020-03-12 04:30:00  0.798
#>  6 05:30    2020-03-12 05:30:00 -0.620
#>  7 06:30    2020-03-12 06:30:00  0.213
#>  8 07:30    2020-03-12 07:30:00  1.21 
#>  9 08:30    2020-03-12 08:30:00  0.370
#> 10 09:30    2020-03-12 09:30:00  0.497
#> # … with 14 more rows

ggplot(df, aes(x = time, y = value)) +
  geom_line() +
  scale_x_datetime(date_labels = "%H:%M")

^{Created on 2020-03-12 by the reprex package (v0.3.0)}

Convert JSON string to JSON object using R

I find myself doing toJSON(fromJSON(jsonStr)) every time I want to pass a JSON string just to change it's class to json.

The idiomatic way to change the class of an object is:

class(jsonStr) <- "json"

To make sure the string is valid, might want to use jsonlite::validate(jsonStr) after assigning the class.(Thanks to @SybolixAU for pointing this out.)

Convert string to a variable name

assign is what you are looking for.

assign("x", 5)

x
[1] 5

but buyer beware.

See R FAQ 7.21
http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-can-I-turn-a-string-into-a-variable_003f

Convert any R variable's value to string

Try capture.output. It's essentially your rawString, but built in.

capture.output(myFunc)
[1] "function(x) { x + 1}"

Unfortunately I can't speak for sparkTable as I don't have it.

You might also consider ?dput, which is a good way to provide something for users to copy-paste into their consoles to recreate your variable, though doesn't convert to string (e.g. dput(iris) --> if I were to copy-paste this into my terminal I'd get exactly what you got).

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