# List Vol.2: solutions

Below are the solutions to these exercises on list vol. 2.

```####################
#                  #
#    Exercise 1    #
#                  #
####################
#Consider 3 vectors, day, month and year:

year=c(2005:2016)
month=c(1:12)
day=c(1:31)

#Define a list Date such as:
#Date=
#\$year
#[1] 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
#\$month
# [1]  1  2  3  4  5  6  7  8  9 10 11 12
#\$day
# [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Date=list()
Date\$year=year
Date\$month=month
Date\$day=day
Date
```
```## \$year
##  [1] 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
##
## \$month
##  [1]  1  2  3  4  5  6  7  8  9 10 11 12
##
## \$day
##  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
## [24] 24 25 26 27 28 29 30 31
```
```####################
#                  #
#    Exercise 2    #
#                  #
####################
#write an R statement that will replace the values of year element in Date list for c(2000:2010)

Date\$year=c(2000:2010)
Date
```
```## \$year
##  [1] 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
##
## \$month
##  [1]  1  2  3  4  5  6  7  8  9 10 11 12
##
## \$day
##  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
## [24] 24 25 26 27 28 29 30 31
```
```####################
#                  #
#    Exercise 3    #
#                  #
####################
#write an R statement that will delete the value 4 of the month component of the list Date.

Date\$month=Date\$month[-4]
Date
```
```## \$year
##  [1] 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
##
## \$month
##  [1]  1  2  3  5  6  7  8  9 10 11 12
##
## \$day
##  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
## [24] 24 25 26 27 28 29 30 31
```
```####################
#                  #
#    Exercise 4    #
#                  #
####################
#Consider a vector x such that:

x=c(1,3,4,7,11,18,29)

#Write an R statement that will return a list with components of value:
#x*2,x/2,sqrt(x) and names "x*2","x/2","sqrt(x)"

X2=list('x*2'=x*2,'x/2'=x/2,'sqrt(x)'=sqrt(x))
X2
```
```## \$`x*2`
## [1]  2  6  8 14 22 36 58
##
## \$`x/2`
## [1]  0.5  1.5  2.0  3.5  5.5  9.0 14.5
##
## \$`sqrt(x)`
## [1] 1.000000 1.732051 2.000000 2.645751 3.316625 4.242641 5.385165
```
```####################
#                  #
#    Exercise 5    #
#                  #
####################
#Consider the X2 list.
#Write an R statement that will return a vector:
#2.000000 2.645751 3.316625

X2[[3]][3:5]
```
```## [1] 2.000000 2.645751 3.316625
```
```####################
#                  #
#    Exercise 6    #
#                  #
####################
#Write an R statement that will return a concatenation of Date and X2 lists.

M=c(Date,X2)
M
```
```## \$year
##  [1] 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
##
## \$month
##  [1]  1  2  3  5  6  7  8  9 10 11 12
##
## \$day
##  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
## [24] 24 25 26 27 28 29 30 31
##
## \$`x*2`
## [1]  2  6  8 14 22 36 58
##
## \$`x/2`
## [1]  0.5  1.5  2.0  3.5  5.5  9.0 14.5
##
## \$`sqrt(x)`
## [1] 1.000000 1.732051 2.000000 2.645751 3.316625 4.242641 5.385165
```
```####################
#                  #
#    Exercise 7    #
#                  #
####################
#Write an R statement that will return a sublist N of M, with components year,x*2 and day.

N=M[c('year','x*2','day')]
N
```
```## \$year
##  [1] 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
##
## \$`x*2`
## [1]  2  6  8 14 22 36 58
##
## \$day
##  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
## [24] 24 25 26 27 28 29 30 31
```
```####################
#                  #
#    Exercise 8    #
#                  #
####################
#Consider the N list.
#Write an R statement that will return:
#-the length of x*2 vector in N
#-the value of the second element of vector year in N

length(N[[2]])
```
```## [1] 7
```
```N\$year[2]
```
```## [1] 2001
```
```####################
#                  #
#    Exercise 9    #
#                  #
####################
#Consider 3 letters vectors, and 2 numeric vectors:
A=letters[1:4];B=letters[5:10];C=letters[11:15]

D=c(1:10);E=c(20:5)

#Define a list z, with elementes x and y,such that
#x is a list  with elements A,B,and C.
#and y is alist with elements D and E.

x=list(A,B,C)

y=list(D,E)

z=list(x,y)

z
```
```## \$X
## \$X\$A
##  [1]  1  2  3  4  5  6  7  8  9 10
##
## \$X\$B
##  [1] 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5
##
##
## \$Y
## \$Y\$A
## [1] "a" "b" "c" "d"
##
## \$Y\$B
## [1] "e" "f" "g" "h" "i" "j"
##
## \$Y\$C
## [1] "k" "l" "m" "n" "o"
```
```####################
#                  #
#    Exercise 10   #
#                  #
####################
#Write an R statement that will return:
#-the number on third position on the second vector of the first list of z
#-the letter on fifth position on the third vector of the second list of z

z[[1]][[2]][3]
```
```## [1] 18
```
```z[[2]][[3]][5]
```
```## [1] "o"
```