## Note: this set of examples is is certainly non-exhaustive and does not
## showcase many recent features, but remains a very good starting point
## Let's start with some statistical programming
v <- iris$Sepal.Length
d <- num_vars(iris) # Saving numeric variables
f <- iris$Species # Factor
# Simple statistics
fmean(v) # vector
fmean(qM(d)) # matrix (qM is a faster as.matrix)
fmean(d) # data.frame
# Preserving data structure
fmean(qM(d), drop = FALSE) # Still a matrix
fmean(d, drop = FALSE) # Still a data.frame
# Weighted statistics, supported by most functions...
w <- abs(rnorm(fnrow(iris)))
fmean(d, w = w)
# Grouped statistics...
fmean(d, f)
# Groupwise-weighted statistics...
fmean(d, f, w)
# Simple Transformations...
head(fmode(d, TRA = "replace")) # Replacing values with the mode
head(fmedian(d, TRA = "-")) # Subtracting the median
head(fsum(d, TRA = "%")) # Computing percentages
head(fsd(d, TRA = "/")) # Dividing by the standard-deviation (scaling), etc...
# Weighted Transformations...
head(fnth(d, 0.75, w = w, TRA = "replace")) # Replacing by the weighted 3rd quartile
# Grouped Transformations...
head(fvar(d, f, TRA = "replace")) # Replacing values with the group variance
head(fsd(d, f, TRA = "/")) # Grouped scaling
head(fmin(d, f, TRA = "-")) # Setting the minimum value in each species to 0
head(fsum(d, f, TRA = "/")) # Dividing by the sum (proportions)
head(fmedian(d, f, TRA = "-")) # Groupwise de-median
head(ffirst(d, f, TRA = "%%")) # Taking modulus of first group-value, etc. ...
# Grouped and weighted transformations...
head(fsd(d, f, w, "/"), 3) # weighted scaling
head(fmedian(d, f, w, "-"), 3) # subtracting the weighted group-median
head(fmode(d, f, w, "replace"), 3) # replace with weighted statistical mode
## Some more advanced transformations...
head(fbetween(d)) # Averaging (faster t.: fmean(d, TRA = "replace"))
head(fwithin(d)) # Centering (faster than: fmean(d, TRA = "-"))
head(fwithin(d, f, w)) # Grouped and weighted (same as fmean(d, f, w, "-"))
head(fwithin(d, f, w, mean = 5)) # Setting a custom mean
head(fwithin(d, f, w, theta = 0.76)) # Quasi-centering i.e. d - theta*fbetween(d, f, w)
head(fwithin(d, f, w, mean = "overall.mean")) # Preserving the overall mean of the data
head(fscale(d)) # Scaling and centering
head(fscale(d, mean = 5, sd = 3)) # Custom scaling and centering
head(fscale(d, mean = FALSE, sd = 3)) # Mean preserving scaling
head(fscale(d, f, w)) # Grouped and weighted scaling and centering
head(fscale(d, f, w, mean = 5, sd = 3)) # Custom grouped and weighted scaling and centering
head(fscale(d, f, w, mean = FALSE, # Preserving group means
sd = "within.sd")) # and setting group-sd to fsd(fwithin(d, f, w), w = w)
head(fscale(d, f, w, mean = "overall.mean", # Full harmonization of group means and variances,
sd = "within.sd")) # while preserving the level and scale of the data.
head(get_vars(iris, 1:2)) # Use get_vars for fast selecting, gv is shortcut
head(fhdbetween(gv(iris, 1:2), gv(iris, 3:5))) # Linear prediction with factors and covariates
head(fhdwithin(gv(iris, 1:2), gv(iris, 3:5))) # Linear partialling out factors and covariates
ss(iris, 1:10, 1:2) # Similarly fsubset/ss for fast subsetting rows
# Simple Time-Computations..
head(flag(AirPassengers, -1:3)) # One lead and three lags
head(fdiff(EuStockMarkets, # Suitably lagged first and second differences
c(1, frequency(EuStockMarkets)), diff = 1:2))
head(fdiff(EuStockMarkets, rho = 0.87)) # Quasi-differences (x_t - rho*x_t-1)
head(fdiff(EuStockMarkets, log = TRUE)) # Log-differences
head(fgrowth(EuStockMarkets)) # Exact growth rates (percentage change)
head(fgrowth(EuStockMarkets, logdiff = TRUE)) # Log-difference growth rates (percentage change)
# Note that it is not necessary to use factors for grouping.
fmean(gv(mtcars, -c(2,8:9)), mtcars$cyl) # Can also use vector (internally converted using qF())
fmean(gv(mtcars, -c(2,8:9)),
gv(mtcars, c(2,8:9))) # or a list of vector (internally grouped using GRP())
g <- GRP(mtcars, ~ cyl + vs + am) # It is also possible to create grouping objects
print(g) # These are instructive to learn about the grouping,
plot(g) # and are directly handed down to C++ code
fmean(gv(mtcars, -c(2,8:9)), g) # This can speed up multiple computations over same groups
fsd(gv(mtcars, -c(2,8:9)), g)
# Factors can efficiently be created using qF()
f1 <- qF(mtcars$cyl) # Unlike GRP objects, factors are checked for NA's
f2 <- qF(mtcars$cyl, na.exclude = FALSE) # This can however be avoided through this option
class(f2) # Note the added class
library(microbenchmark)
microbenchmark(fmean(mtcars, f1), fmean(mtcars, f2)) # A minor difference, larger on larger data
with(mtcars, finteraction(cyl, vs, am)) # Efficient interactions of vectors and/or factors
finteraction(gv(mtcars, c(2,8:9))) # .. or lists of vectors/factors
# Simple row- or column-wise computations on matrices or data frames with dapply()
dapply(mtcars, quantile) # column quantiles
dapply(mtcars, quantile, MARGIN = 1) # Row-quantiles
# dapply preserves the data structure of any matrices / data frames passed
# Some fast matrix row/column functions are also provided by the matrixStats package
# Similarly, BY performs grouped comptations
BY(mtcars, f2, quantile)
BY(mtcars, f2, quantile, expand.wide = TRUE)
# For efficient (grouped) replacing and sweeping out computed statistics, use TRA()
sds <- fsd(mtcars)
head(TRA(mtcars, sds, "/")) # Simple scaling (if sd's not needed, use fsd(mtcars, TRA = "/"))
microbenchmark(TRA(mtcars, sds, "/"), sweep(mtcars, 2, sds, "/")) # A remarkable performance gain..
sds <- fsd(mtcars, f2)
head(TRA(mtcars, sds, "/", f2)) # Groupd scaling (if sd's not needed: fsd(mtcars, f2, TRA = "/"))
# All functions above perserve the structure of matrices / data frames
# If conversions are required, use these efficient functions:
mtcarsM <- qM(mtcars) # Matrix from data.frame
head(qDF(mtcarsM)) # data.frame from matrix columns
head(mrtl(mtcarsM, TRUE, "data.frame")) # data.frame from matrix rows, etc..
head(qDT(mtcarsM, "cars")) # Saving row.names when converting matrix to data.table
head(qDT(mtcars, "cars")) # Same use a data.frame
## Now let's get some real data and see how we can use this power for data manipulation
head(wlddev) # World Bank World Development Data: 216 countries, 61 years, 5 series (columns 9-13)
# Starting with some discriptive tools...
namlab(wlddev, class = TRUE) # Show variable names, labels and classes
fnobs(wlddev) # Observation count
pwnobs(wlddev) # Pairwise observation count
head(fnobs(wlddev, wlddev$country)) # Grouped observation count
fndistinct(wlddev) # Distinct values
descr(wlddev) # Describe data
varying(wlddev, ~ country) # Show which variables vary within countries
qsu(wlddev, pid = ~ country, # Panel-summarize columns 9 though 12 of this data
cols = 9:12, vlabels = TRUE) # (between and within countries)
qsu(wlddev, ~ region, ~ country, # Do all of that by region and also compute higher moments
cols = 9:12, higher = TRUE) # -> returns a 4D array
qsu(wlddev, ~ region, ~ country, cols = 9:12,
higher = TRUE, array = FALSE) |> # Return as a list of matrices..
unlist2d(c("Variable","Trans"), row.names = "Region") |> head()# and turn into a tidy data.frame
pwcor(num_vars(wlddev), P = TRUE) # Pairwise correlations with p-value
pwcor(fmean(num_vars(wlddev), wlddev$country), P = TRUE) # Correlating country means
pwcor(fwithin(num_vars(wlddev), wlddev$country), P = TRUE) # Within-country correlations
psacf(wlddev, ~country, ~year, cols = 9:12) # Panel-data Autocorrelation function
pspacf(wlddev, ~country, ~year, cols = 9:12) # Partial panel-autocorrelations
psmat(wlddev, ~iso3c, ~year, cols = 9:12) |> plot() # Convert panel to 3D array and plot
## collapse offers a few very efficent functions for data manipulation:
# Fast selecting and replacing columns
series <- get_vars(wlddev, 9:12) # Same as wlddev[9:12] but 2x faster
series <- fselect(wlddev, PCGDP:ODA) # Same thing: > 100x faster than dplyr::select
get_vars(wlddev, 9:12) <- series # Replace, 8x faster wlddev[9:12] <- series + replaces names
fselect(wlddev, PCGDP:ODA) <- series # Same thing
# Fast subsetting
head(fsubset(wlddev, country == "Ireland", -country, -iso3c))
head(fsubset(wlddev, country == "Ireland" & year > 1990, year, PCGDP:ODA))
ss(wlddev, 1:10, 1:10) # This is an order of magnitude faster than wlddev[1:10, 1:10]
# Fast transforming
head(ftransform(wlddev, ODA_GDP = ODA / PCGDP, ODA_LIFEEX = sqrt(ODA) / LIFEEX))
settransform(wlddev, ODA_GDP = ODA / PCGDP, ODA_LIFEEX = sqrt(ODA) / LIFEEX) # by reference
head(ftransform(wlddev, PCGDP = NULL, ODA = NULL, GINI_sum = fsum(GINI)))
head(ftransformv(wlddev, 9:12, log)) # Can also transform with lists of columns
head(ftransformv(wlddev, 9:12, fscale, apply = FALSE)) # apply = FALSE invokes fscale.data.frame
settransformv(wlddev, 9:12, fscale, apply = FALSE) # Changing the data by reference
ftransform(wlddev) <- fscale(gv(wlddev, 9:12)) # Same thing (using replacement method)
library(magrittr) # Same thing, using magrittr
wlddev %<>% ftransformv(9:12, fscale, apply = FALSE)
wlddev %>% ftransform(gv(., 9:12) |> # With compound pipes: Scaling and lagging
fscale() |> flag(0:2, iso3c, year)) |> head()
# Fast reordering
head(roworder(wlddev, -country, year))
head(colorder(wlddev, country, year))
# Fast renaming
head(frename(wlddev, country = Ctry, year = Yr))
setrename(wlddev, country = Ctry, year = Yr) # By reference
head(frename(wlddev, tolower, cols = 9:12))
# Fast grouping
fgroup_by(wlddev, Ctry, decade) |> fgroup_vars() |> head()
rm(wlddev) # .. but only works with collapse functions
## Now lets start putting things together
wlddev |> fsubset(year > 1990, region, income, PCGDP:ODA) |>
fgroup_by(region, income) |> fmean() # Fast aggregation using the mean
# Same thing using dplyr manipulation verbs
library(dplyr)
wlddev |> filter(year > 1990) |> select(region, income, PCGDP:ODA) |>
group_by(region,income) |> fmean() # This is already a lot faster than summarize_all(mean)
wlddev |> fsubset(year > 1990, region, income, PCGDP:POP) |>
fgroup_by(region, income) |> fmean(POP) # Weighted group means
wlddev |> fsubset(year > 1990, region, income, PCGDP:POP) |>
fgroup_by(region, income) |> fsd(POP) # Weighted group standard deviations
wlddev |> na_omit(cols = "POP") |> fgroup_by(region, income) |>
fselect(PCGDP:POP) |> fnth(0.75, POP) # Weighted group third quartile
wlddev |> fgroup_by(country) |> fselect(PCGDP:ODA) |>
fwithin() |> head() # Within transformation
wlddev |> fgroup_by(country) |> fselect(PCGDP:ODA) |>
fmedian(TRA = "-") |> head() # Grouped centering using the median
# Replacing data points by the weighted first quartile:
wlddev |> na_omit(cols = "POP") |> fgroup_by(country) |>
fselect(country, year, PCGDP:POP) %>%
ftransform(fselect(., -country, -year) |>
fnth(0.25, POP, "fill")) |> head()
wlddev |> fgroup_by(country) |> fselect(PCGDP:ODA) |> fscale() |> head() # Standardizing
wlddev |> fgroup_by(country) |> fselect(PCGDP:POP) |>
fscale(POP) |> head() # Weighted..
wlddev |> fselect(country, year, PCGDP:ODA) |> # Adding 1 lead and 2 lags of each variable
fgroup_by(country) |> flag(-1:2, year) |> head()
wlddev |> fselect(country, year, PCGDP:ODA) |> # Adding 1 lead and 10-year growth rates
fgroup_by(country) |> fgrowth(c(0:1,10), 1, year) |> head()
# etc...
# Aggregation with multiple functions
wlddev |> fsubset(year > 1990, region, income, PCGDP:ODA) |>
fgroup_by(region, income) %>% {
add_vars(fgroup_vars(., "unique"),
fmedian(., keep.group_vars = FALSE) |> add_stub("median_"),
fmean(., keep.group_vars = FALSE) |> add_stub("mean_"),
fsd(., keep.group_vars = FALSE) |> add_stub("sd_"))
} |> head()
# Transformation with multiple functions
wlddev |> fselect(country, year, PCGDP:ODA) |>
fgroup_by(country) %>% {
add_vars(fdiff(., c(1,10), 1, year) |> flag(0:2, year), # Sequence of lagged differences
ftransform(., fselect(., PCGDP:ODA) |> fwithin() |> add_stub("W.")) |>
flag(0:2, year, keep.ids = FALSE)) # Sequence of lagged demeaned vars
} |> head()
# With ftransform, can also easily do one or more grouped mutations on the fly..
settransform(wlddev, median_ODA = fmedian(ODA, list(region, income), TRA = "fill"))
settransform(wlddev, sd_ODA = fsd(ODA, list(region, income), TRA = "fill"),
mean_GDP = fmean(PCGDP, country, TRA = "fill"))
wlddev %<>% ftransform(fmedian(list(median_ODA = ODA, median_GDP = PCGDP),
list(region, income), TRA = "fill"))
# On a groped data frame it is also possible to grouped transform certain columns
# but perform aggregate operatins on others:
wlddev |> fgroup_by(region, income) %>%
ftransform(gmedian_GDP = fmedian(PCGDP, GRP(.), TRA = "replace"),
omedian_GDP = fmedian(PCGDP, TRA = "replace"), # "replace" preserves NA's
omedian_GDP_fill = fmedian(PCGDP)) |> tail()
rm(wlddev)
## For multi-type data aggregation, the function collap() offers ease and flexibility
# Aggregate this data by country and decade: Numeric columns with mean, categorical with mode
head(collap(wlddev, ~ country + decade, fmean, fmode))
# taking weighted mean and weighted mode:
head(collap(wlddev, ~ country + decade, fmean, fmode, w = ~ POP, wFUN = fsum))
# Multi-function aggregation of certain columns
head(collap(wlddev, ~ country + decade,
list(fmean, fmedian, fsd),
list(ffirst, flast), cols = c(3,9:12)))
# Customized Aggregation: Assign columns to functions
head(collap(wlddev, ~ country + decade,
custom = list(fmean = 9:10, fsd = 9:12, flast = 3, ffirst = 6:8)))
# For grouped data frames use collapg
wlddev |> fsubset(year > 1990, country, region, income, PCGDP:ODA) |>
fgroup_by(country) |> collapg(fmean, ffirst) |>
ftransform(AMGDP = PCGDP > fmedian(PCGDP, list(region, income), TRA = "fill"),
AMODA = ODA > fmedian(ODA, income, TRA = "replace_fill")) |> head()
## Additional flexibility for data transformation tasks is offerend by tidy transformation operators
# Within-transformation (centering on overall mean)
head(W(wlddev, ~ country, cols = 9:12, mean = "overall.mean"))
# Partialling out country and year fixed effects
head(HDW(wlddev, PCGDP + LIFEEX ~ qF(country) + qF(year)))
# Same, adding ODA as continuous regressor
head(HDW(wlddev, PCGDP + LIFEEX ~ qF(country) + qF(year) + ODA))
# Standardizing (scaling and centering) by country
head(STD(wlddev, ~ country, cols = 9:12))
# Computing 1 lead and 3 lags of the 4 series
head(L(wlddev, -1:3, ~ country, ~year, cols = 9:12))
# Computing the 1- and 10-year first differences
head(D(wlddev, c(1,10), 1, ~ country, ~year, cols = 9:12))
head(D(wlddev, c(1,10), 1:2, ~ country, ~year, cols = 9:12)) # ..first and second differences
# Computing the 1- and 10-year growth rates
head(G(wlddev, c(1,10), 1, ~ country, ~year, cols = 9:12))
# Adding growth rate variables to dataset
add_vars(wlddev) <- G(wlddev, c(1, 10), 1, ~ country, ~year, cols = 9:12, keep.ids = FALSE)
get_vars(wlddev, "G1.", regex = TRUE) <- NULL # Deleting again
# These operators can conveniently be used in regression formulas:
# Using a Mundlak (1978) procedure to estimate the effect of OECD on LIFEEX, controlling for PCGDP
lm(LIFEEX ~ log(PCGDP) + OECD + B(log(PCGDP), country),
wlddev |> fselect(country, OECD, PCGDP, LIFEEX) |> na_omit())
# Adding 10-year lagged life-expectancy to allow for some convergence effects (dynamic panel model)
lm(LIFEEX ~ L(LIFEEX, 10, country) + log(PCGDP) + OECD + B(log(PCGDP), country),
wlddev |> fselect(country, OECD, PCGDP, LIFEEX) |> na_omit())
# Tranformation functions and operators also support indexed data classes:
wldi <- findex_by(wlddev, country, year)
head(W(wldi$PCGDP)) # Country-demeaning
head(W(wldi, cols = 9:12))
head(W(wldi$PCGDP, effect = 2)) # Time-demeaning
head(W(wldi, effect = 2, cols = 9:12))
head(HDW(wldi$PCGDP)) # Country- and time-demeaning
head(HDW(wldi, cols = 9:12))
head(STD(wldi$PCGDP)) # Standardizing by country
head(STD(wldi, cols = 9:12))
head(L(wldi$PCGDP, -1:3)) # Panel-lags
head(L(wldi, -1:3, 9:12))
head(G(wldi$PCGDP)) # Panel-Growth rates
head(G(wldi, 1, 1, 9:12))
lm(Dlog(PCGDP) ~ L(Dlog(LIFEEX), 0:3), wldi) # Panel data regression
rm(wldi)
# Remove all objects used in this example section
rm(v, d, w, f, f1, f2, g, mtcarsM, sds, series, wlddev)
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