The first steps
Logarithm
the logarithm of a number is the exponent to which another fixed number, the base, must be raised to produce that number
\(\log_2 8 = 3\)
\(2^3 = 8\)
Do not confuse == with = or <-!
Atomic vector
Atomic vector
Coercion
У R есть иерархия coercion: NULL < raw < logical < integer < double < complex < character < list < expression
Task
Create a vector:
vv <- 11:30
Return only even numbers from it! Solutions
vv[c(2,4,6,8,10,12,14,16,18,20)]
## [1] 12 14 16 18 20 22 24 26 28 30
vv[1:10*2]
## [1] 12 14 16 18 20 22 24 26 28 30
vv[c(FALSE, TRUE)]
## [1] 12 14 16 18 20 22 24 26 28 30
Task
Create a vector:
vv <- c(1:4, 56:53, 13:16)
Return values that are more than the mean of this vector! Solution
vv[vv>mean(vv)]
## [1] 56 55 54 53
Task
Try to calculate the mean of this vector (without NA!)
There are at least two solutions! Solutions
mean(vv[!is.na(vv)])
## [1] 20.90909
mean(vv, na.rm = TRUE) #Read help!
## [1] 20.90909
Matrices
Conclusion
Thank you!
