1.str() In many languages, other types can be converted into strings, but the data type is returned in R.

data(iris)
str(iris)

Return:'data.frame': 100 obs. of 5 variables: $ Sepal.Length: num 7 6.4 6.9 5.5 6.5 5.7 6.3 4.9 6.6 5.2 ... $ Sepal.Width: num 3.2 3.2 3.1 2.3 2.8 2.8 3.3 2.4 2.9 2.7 ... $ Petal.Length: num 4.7 4.5 4.9 4 4.6 4.5 4.7 3.3 4.6 3.9 ... $ Petal.Width: num 1.4 1.5 1.5 1.3 1.5 1.3 1.6 1 1.3 1.4 ... $ Species: Factor w/2 levels " versicolor","virginica": 1 1 1 1 1 1 1 1 1 1 ...

2. Read data through the link

site <- "http://random.org/integers/" # This is a website that generates random numbers
# Generate two columns of 10 rows of random numbers, the minimum value is 100, the maximum value is 200
query <- "num=10&min=100&max=200&col=2&base=10&format=plain&rnd=new"
txt <- paste(site, query, sep="?") # URL
nums <- read.table(file=txt) # read

3. Backticks

df <- data.frame(x=rnorm(5),y=runif(5))
names(df) <- 1:2

Take the first column, if so, an error will be reported:

df$1

Report an "error: unexpected numeric constant in "df$1"" error.

But this works:

df$`1`

There will also be backticks when the tab key is prompted after df$.

It is also possible to do linear regression:

lm(`2`~`1`,data=df)

4. Operations on the data frame

New data:

sales <- expand.grid(country = c('USA','UK','FR'),
                     product = c(1, 2, 3))
sales$revenue <- rnorm(dim(sales)[1], mean=100, sd=10)

Transform to increase the column:

usd2eur <- 1.5
transform(sales, euro = revenue * usd2eur)

5. Cut/table cut can divide the data into the desired interval:

irisSL <- iris$Sepal.Length
# Divide into five bins
cut(irisSL, 5)
# It can also be divided according to the range we want
cut(irisSL, breaks = seq(1,8,1))

You can use the table to count the number of each range:

table(cut(irisSL, 5))

Returns: (4.9,5.5] (5.5,6.1] (6.1,6.7] (6.7,7.3] (7.3,7.9] 12 33 35 13 7

Welcome to pay attention~

Shengxin programming daily