| Function/operator | Brief description |
|---|---|
| if( ){ } | Conditional check |
| if( ){ } else { } | Check and alternative |
| ifelse | Element-wise if-else check |
| switch | Multiple if choices |
| for( ){ } | Iterative loop |
| while( ){ } | Conditional loop |
| apply | Implicit loop by margin |
| tapply | Implicit loop by factor |
| lapply | Implicit loop by member |
| sapply | As lapply, array returned |
| break | Exit explicit loop Section |
| next | Skip to next loop iteration |
| repeat{ } | Repeat code until break |
Crie os seguintes vetores:
vec1 <- c(2,1,1,3,2,1,0) vec2 <- c(3,8,2,2,0,0,0)
Sem executá-los, determine qual dos seguintes if statements resultariam em um string sendo impresso no console. Em seguinda, confirme suas respostas.
vec2[3] não é NA.vec1 <- c(2,1,1,3,2,1,0)
vec2 <- c(3,8,2,2,0,0,0)
if((vec1[1]+vec2[2])==10){ cat("Print me!") }## Print me!if(vec1[1]>=2&&vec2[1]>=2){ cat("Print me!") }## Print me!if(all((vec2-vec1)[c(2,6)]<7)){ cat("Print me!") } #não imprime
if(!is.na(vec2[3])){ cat("Print me!") }## Print me!Usando os mesmos vetores, escreva e execute a linha de código que multiplica os elementos correspondentes dos dois vetores se sua soma for maior que 3. Caso contrário, o código deve simplesmente somar os elementos.
vec3 <- (vec1+vec2) >=3
ifelse(vec3 == 1, vec1*vec2, vec1+vec2)## [1] 6 8 2 6 2 1 0No editor, escreva código que tome uma matriz quadrada de caracteres e checa se qualquer dos strings na diagonal principal começam com a letra g, maiúscula ou minúscula. Se satisfeito, essas entradas devem ser sobrescritas com “HERE”. Caso contrário, a matriz inteira deve ser substituída com uma matriz identidade com as mesmas dimensões.
acha_g <- function(x){
#identifica se existe um g
test <- ifelse(grepl(pattern = "^g|G",diag(x)) == TRUE, "HERE", diag(x))
#se sim, o elemento 'e substituido por here
if("HERE" %in% test){
diag(x) <- test
return(x)
# caso contrario, matriz identidade
}else{
return(diag(dim(x)[1]))}
}
#i
mymat <- matrix(as.character(1:16),4,4)
acha_g(mymat)## [,1] [,2] [,3] [,4]
## [1,] 1 0 0 0
## [2,] 0 1 0 0
## [3,] 0 0 1 0
## [4,] 0 0 0 1#ii
mymat <- matrix(c("DANDELION","Hyacinthus","Gerbera",
"MARIGOLD","geranium","ligularia",
"Pachysandra","SNAPDRAGON","GLADIOLUS"),3,3)
acha_g(mymat)## [,1] [,2] [,3]
## [1,] "DANDELION" "MARIGOLD" "Pachysandra"
## [2,] "Hyacinthus" "HERE" "SNAPDRAGON"
## [3,] "Gerbera" "ligularia" "HERE"#iii
mymat <- matrix(c("GREAT","exercises","right","here"),2,2,
byrow=T)
acha_g(mymat)## [,1] [,2]
## [1,] "HERE" "exercises"
## [2,] "right" "here"
Condições if empilhadas que realizem o mesmo que o switch a seguir:
R> mynum <- 3
R> foo <- switch(mynum,12,34,56,78,NA
R> foo
[1] 56
stack <- function(x){
if (x == 1) {foo <<- 12 # <<- operador para atingir variável do escopo global
} else if (x == 2) {foo <<- 34
} else if (x == 3) {foo <<- 56
} else if (x == 4) {foo <<- 78
} else if (x == 5) {foo <<- NA
} else {foo <<- NULL}
print(foo)
}
mynum <- 3
stack(mynum)## [1] 56stack(0) # equivalente a mynum <- 0## NULL#define a funcao
condicionais <- function(){
if ("High" %in% doselevel){
if (lowdose >= 10){ lowdose <- 10
} else {lowdose <- lowdose/2}
if (meddose >= 26) { meddose <- 26 }
if (highdose < 60) { highdose <- 60 } else {highdose <- highdose *1.5}
dosage <<- c(rep(lowdose, length(doselevel)))
dosage[which(doselevel == "Med")] <<- meddose
dosage[which(doselevel == "High")] <<- highdose
} else {
doselevel <<- factor(doselevel, levels = c("Low", "Med"), labels = c("Small", "Large"))
if (lowdose < 15 & meddose < 35) {
lowdose <- lowdose*2
meddose <- meddose + highdose}
dosage <<- c(rep(lowdose, length(doselevel)))
dosage[which(doselevel == "Large")] <<- meddose
}
}
#i
lowdose <- 12.5
meddose <- 25.3
highdose <- 58.1
doselevel <- factor(c("Low","High","High","High","Low","Med",
"Med"),levels=c("Low","Med","High"))
condicionais()
dosage## [1] 10.0 60.0 60.0 60.0 10.0 25.3 25.3#ii
lowdose <- 12.5
meddose <- 25.3
highdose <- 58.1
doselevel <- factor(c("Low","Low","Low","Med","Low","Med",
"Med"),levels=c("Low","Med","High"))
condicionais()
dosage## [1] 25.0 25.0 25.0 83.4 25.0 83.4 83.4doselevel## [1] Small Small Small Large Small Large Large
## Levels: Small Large#iii
lowdose <- 9
meddose <- 49
highdose <- 61
doselevel <- factor(c("Low","Med","Med"),
levels=c("Low","Med","High"))
condicionais()
dosage## [1] 9 49 49doselevel## [1] Small Large Large
## Levels: Small Large#iv
lowdose <- 9
meddose <- 49
highdose <- 61
doselevel <- factor(c("Low","High","High","High","Low","Med",
"Med"),levels=c("Low","Med","High"))
condicionais()
dosage## [1] 4.5 91.5 91.5 91.5 4.5 26.0 26.0mynum <- sample(0:9, size = 1)
switcharoo <- function(x){
switch(x+1, 'zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine') %>%
print()
}
for (i in 1:5) {
mynum <- sample(0:9, size = 1)
print(mynum)
switcharoo(mynum)
}## [1] 0
## [1] "zero"
## [1] 1
## [1] "one"
## [1] 8
## [1] "eight"
## [1] 8
## [1] "eight"
## [1] 9
## [1] "nine"
loopvec1 <- 5:7
loopvec2 <- 9:6
foo <- matrix(NA,length(loopvec1),length(loopvec2))
for(i in 1:length(loopvec1)){
foo[i,] <- loopvec1[i]*loopvec2
}
foo## [,1] [,2] [,3] [,4]
## [1,] 45 40 35 30
## [2,] 54 48 42 36
## [3,] 63 56 49 42# switch(EXPR=mystring,Homer=12,Marge=34,Bart=56,Lisa=78,Maggie=90,
# NA)
vec <- c("Peter","Homer","Lois","Stewie","Maggie","Bart")
vec_int <- NA
for (i in 1:length(vec)){
vec_int[i] <- switch(EXPR=vec[i],Homer=12,Marge=34,Bart=56,Lisa=78,Maggie=90,
NA)
}
vec_int## [1] NA 12 NA NA 90 56contador <- function(list){
counter <- 0
for (i in 1:length(list)){ #itera sobre os itens da lista principal
member <- list[[i]] #toma como member o elemento i da lista principal
if (is.matrix(member)){ #incrementa se o elemento for uma matriz
counter <- counter+1
}
if (is.list(member)){ #itera sobre os elementos da lista principal que
#sao listas
for (j in 1:length(member)){
if(is.matrix(member[[j]])){
counter <- counter+1
}
}
}
}
return(counter)
}
#i
mylist <- list(aa=c(3.4,1),bb=matrix(1:4,2,2),
cc=matrix(c(T,T,F,T,F,F),3,2),dd="string here",
ee=list(c("hello","you"),matrix(c("hello",
"there"))),
ff=matrix(c("red","green","blue","yellow")))
contador(mylist)## [1] 4#ii
mylist <- list("tricked you",as.vector(matrix(1:6,3,2)))
contador(mylist)## [1] 0#iii
mylist <- list(list(1,2,3),list(c(3,2),2),
list(c(1,2),matrix(c(1,2))),
rbind(1:10,100:91))
contador(mylist)## [1] 2
mylist <- list()
counter <- 1
mynumbers <- c(4,5,1,2,6,2,4,6,6,2)
mycondition <- mynumbers[counter]<=5
while(mycondition){
mylist[[counter]] <- diag(mynumbers[counter])
counter <- counter+1
if(counter<=length(mynumbers)){
mycondition <- mynumbers[counter]<=5
} else {
mycondition <- FALSE
}
}
# i. deve imprimir todas as matrizes ja que todos os elementos sao <= 5
mynumbers <- c(2,2,2,2,5,2)
mylist <- list()
counter <- 1
mycondition <- mynumbers[counter]<=5
while(mycondition){
mylist[[counter]] <- diag(mynumbers[counter])
counter <- counter+1
if(counter<=length(mynumbers)){
mycondition <- mynumbers[counter]<=5
} else {
mycondition <- FALSE
}
}
mylist## [[1]]
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1
##
## [[2]]
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1
##
## [[3]]
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1
##
## [[4]]
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1
##
## [[5]]
## [,1] [,2] [,3] [,4] [,5]
## [1,] 1 0 0 0 0
## [2,] 0 1 0 0 0
## [3,] 0 0 1 0 0
## [4,] 0 0 0 1 0
## [5,] 0 0 0 0 1
##
## [[6]]
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1# ii. # deve imprimir até o elemento de valor 5
mynumbers <- 2:20
mylist <- list()
counter <- 1
mycondition <- mynumbers[counter]<=5
while(mycondition){
mylist[[counter]] <- diag(mynumbers[counter])
counter <- counter+1
if(counter<=length(mynumbers)){
mycondition <- mynumbers[counter]<=5
} else {
mycondition <- FALSE
}
}
mylist## [[1]]
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1
##
## [[2]]
## [,1] [,2] [,3]
## [1,] 1 0 0
## [2,] 0 1 0
## [3,] 0 0 1
##
## [[3]]
## [,1] [,2] [,3] [,4]
## [1,] 1 0 0 0
## [2,] 0 1 0 0
## [3,] 0 0 1 0
## [4,] 0 0 0 1
##
## [[4]]
## [,1] [,2] [,3] [,4] [,5]
## [1,] 1 0 0 0 0
## [2,] 0 1 0 0 0
## [3,] 0 0 1 0 0
## [4,] 0 0 0 1 0
## [5,] 0 0 0 0 1# iii. #nao deve imprimir nada
mynumbers <- c(10,1,10,1,2)
mylist <- list()
counter <- 1
mycondition <- mynumbers[counter]<=5
while(mycondition){
mylist[[counter]] <- diag(mynumbers[counter])
counter <- counter+1
if(counter<=length(mynumbers)){
mycondition <- mynumbers[counter]<=5
} else {
mycondition <- FALSE
}
}
mylist## list()fact_while <- function(mynum){
if(mynum == 0){mynum <- 1
} else {
mynum <- mynum
counter <-mynum-1
while(counter >= 0){
mynum <- mynum*counter
counter <- counter-1
if(counter == 0){break}
}
}
return(mynum)
}
fact_while(5)## [1] 120fact_while(12)## [1] 479001600fact_while(0)## [1] 1mystring <- "R fever"
index <- 1
ecount <- 0
result <- mystring
while(ecount<2 && index<=nchar(mystring)){
char <- substr(mystring, index, index)
if(char == "E" | char == "e"){
ecount <- ecount+1
}
if(ecount >= 2){
result <- substr(mystring, 0, index-1)
break
}
index <- index+1
result <- substr(mystring, 0, index-1)
}
result## [1] "R fev"#i
mystring <- "beautiful"
index <- 1
ecount <- 0
result <- mystring
while(ecount<2 && index<=nchar(mystring)){
char <- substr(mystring, index, index)
if(char == "E" | char == "e"){
ecount <- ecount+1
}
if(ecount >= 2){
result <- substr(mystring, 0, index-1)
break
}
index <- index+1
result <- substr(mystring, 0, index-1)
}
result## [1] "beautiful"#ii
mystring <- "ECCENTRIC"
index <- 1
ecount <- 0
result <- mystring
while(ecount<2 && index<=nchar(mystring)){
char <- substr(mystring, index, index)
if(char == "E" | char == "e"){
ecount <- ecount+1
}
if(ecount >= 2){
result <- substr(mystring, 0, index-1)
break
}
index <- index+1
result <- substr(mystring, 0, index-1)
}
result## [1] "ECC"#iii
mystring <- "ElAbOrAte"
index <- 1
ecount <- 0
result <- mystring
while(ecount<2 && index<=nchar(mystring)){
char <- substr(mystring, index, index)
if(char == "E" | char == "e"){
ecount <- ecount+1
}
if(ecount >= 2){
result <- substr(mystring, 0, index-1)
break
}
index <- index+1
result <- substr(mystring, 0, index-1)
}
result## [1] "ElAbOrAt"#iv
mystring <-"eeeeek!"
index <- 1
ecount <- 0
result <- mystring
while(ecount<2 && index<=nchar(mystring)){
char <- substr(mystring, index, index)
if(char == "E" | char == "e"){
ecount <- ecount+1
}
if(ecount >= 2){
result <- substr(mystring, 0, index-1)
break
}
index <- index+1
result <- substr(mystring, 0, index-1)
}
result## [1] "e"
apply() - apply a function over a dimension
tapply() - apply a function factoring by a factor variable. Ex: sum of values for different types of a product.
lapply() - apply a function over elements of a list
sapply() - returns lapply() in array form
Arguments of the function applied can be passed as arguments in the ellipses of the apply family.
foo <- matrix(1:12,4,3)
foo <- apply(foo,1,sort,decreasing=TRUE)
apply(foo, 2, sum) #soma das colunas, indicando colunas no segundo argumento## [1] 15 18 21 24matlist <- list(matrix(c(T,F,T,T),2,2),
matrix(c("a","c","b","z","p","q"),3,2),
matrix(1:8,2,4))
matlist # cria 3 matrizes: lógica 2x2, caracteres 3x2, numérica 2x4 ## [[1]]
## [,1] [,2]
## [1,] TRUE TRUE
## [2,] FALSE TRUE
##
## [[2]]
## [,1] [,2]
## [1,] "a" "z"
## [2,] "c" "p"
## [3,] "b" "q"
##
## [[3]]
## [,1] [,2] [,3] [,4]
## [1,] 1 3 5 7
## [2,] 2 4 6 8for(i in 1:length(matlist)){ #loop transpõe cada matriz na lista
matlist[[i]] <- t(matlist[[i]])
}
matlist## [[1]]
## [,1] [,2]
## [1,] TRUE FALSE
## [2,] TRUE TRUE
##
## [[2]]
## [,1] [,2] [,3]
## [1,] "a" "c" "b"
## [2,] "z" "p" "q"
##
## [[3]]
## [,1] [,2]
## [1,] 1 2
## [2,] 3 4
## [3,] 5 6
## [4,] 7 8#resetando a lista
matlist <- list(matrix(c(T,F,T,T),2,2),
matrix(c("a","c","b","z","p","q"),3,2),
matrix(1:8,2,4))
lapply(matlist, t) #aplicar funcao t a cada elemento de matlist## [[1]]
## [,1] [,2]
## [1,] TRUE FALSE
## [2,] TRUE TRUE
##
## [[2]]
## [,1] [,2] [,3]
## [1,] "a" "c" "b"
## [2,] "z" "p" "q"
##
## [[3]]
## [,1] [,2]
## [1,] 1 2
## [2,] 3 4
## [3,] 5 6
## [4,] 7 8qux <- array(96:1,dim=c(4,4,2,3))
# 3 blocos formados de 2 camadas de matrizes 4x4
#i elementos diagonais de todas as matrizes da secunda camada
apply(qux[,,2,], MARGIN = 3, FUN = diag)## [,1] [,2] [,3]
## [1,] 80 48 16
## [2,] 75 43 11
## [3,] 70 38 6
## [4,] 65 33 1#ii
apply(qux[,4,,], MARGIN = 3, dim) %>% #aplica dim() à quarta coluna, por camada resultante do subset qu[,4,,]
apply(MARGIN = 1, sum) #aplica soma por linha## [1] 12 6
next indica que, sob uma determinada condição, o laço deve pular aquela iteração. Está limitado ao escopo da iteração. Por exemplo, se ocorrer em uma iteração aninhada, só pularia uma das subiterações sem comprometer a iteração de escopo superior.
break indica uma parada do processo geral de iteração.
repeat{} é um laço while implícito, que executa iterações dentro das chaves {} até que seja dada uma instrução de interrupção com break
foo <- 5
bar <- c(2,3,1.1,4,0,4.1,3)
# laço while deve produzir loop2.result == 2.500000 1.666667 4.545455 1.250000 NA NA NA
loop2.result <- rep(NA,length(bar))
counter <- 1
mycondition <- (foo/bar)!= Inf
while(mycondition[counter]){
loop2.result[counter] <- (foo/bar)[counter]
counter <- counter+1
}
loop2.result## [1] 2.500000 1.666667 4.545455 1.250000 NA NA NA#i
mynumbers <- c(4,5,1,2,6,2,4,6,6,2)
mylist <- list()
for (i in 1:length(mynumbers)){
if (mynumbers[i] <= 5){
mylist[[i]] <- diag(mynumbers[i])
} else{break}
}
mylist## [[1]]
## [,1] [,2] [,3] [,4]
## [1,] 1 0 0 0
## [2,] 0 1 0 0
## [3,] 0 0 1 0
## [4,] 0 0 0 1
##
## [[2]]
## [,1] [,2] [,3] [,4] [,5]
## [1,] 1 0 0 0 0
## [2,] 0 1 0 0 0
## [3,] 0 0 1 0 0
## [4,] 0 0 0 1 0
## [5,] 0 0 0 0 1
##
## [[3]]
## [,1]
## [1,] 1
##
## [[4]]
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1#ii
mylist <- list()
counter <- 1
repeat{
mylist[[counter]] <- diag(mynumbers[counter])
counter <- counter+1
if(mynumbers[counter] > 5){break}
}
mylist## [[1]]
## [,1] [,2] [,3] [,4]
## [1,] 1 0 0 0
## [2,] 0 1 0 0
## [3,] 0 0 1 0
## [4,] 0 0 0 1
##
## [[2]]
## [,1] [,2] [,3] [,4] [,5]
## [1,] 1 0 0 0 0
## [2,] 0 1 0 0 0
## [3,] 0 0 1 0 0
## [4,] 0 0 0 1 0
## [5,] 0 0 0 0 1
##
## [[3]]
## [,1]
## [1,] 1
##
## [[4]]
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1#i
reslist <- list()
matlist1 <- list(matrix(1:4,2,2),matrix(1:4),matrix(1:8,4,2))
matlist2 <- matlist1
counter <- 1
for (i in 1:length(matlist1)){
for (j in 1:length(matlist2)){
if(ncol(matlist1[[i]]) == nrow(matlist2[[j]])){
reslist[[counter]] <- matlist1[[i]] %*% matlist2[[j]]
counter <- counter+1
} else {
reslist[[counter]] <- "not possible"
counter <- counter+1
}
}
}
reslist## [[1]]
## [,1] [,2]
## [1,] 7 15
## [2,] 10 22
##
## [[2]]
## [1] "not possible"
##
## [[3]]
## [1] "not possible"
##
## [[4]]
## [1] "not possible"
##
## [[5]]
## [1] "not possible"
##
## [[6]]
## [1] "not possible"
##
## [[7]]
## [,1] [,2]
## [1,] 11 23
## [2,] 14 30
## [3,] 17 37
## [4,] 20 44
##
## [[8]]
## [1] "not possible"
##
## [[9]]
## [1] "not possible"#ii
reslist <- list()
matlist1 <- list(matrix(1:4,2,2),matrix(2:5,2,2),matrix(1:16,4,2))
matlist2 <- list(matrix(1:8,2,4),matrix(10:7,2,2),matrix(9:2,4,2))
counter <- 1
for (i in 1:length(matlist1)){
for (j in 1:length(matlist2)){
if(ncol(matlist1[[i]]) == nrow(matlist2[[j]])){
reslist[[counter]] <- matlist1[[i]] %*% matlist2[[j]]
counter <- counter+1
} else {
reslist[[counter]] <- "not possible"
counter <- counter+1
}
}
}
reslist## [[1]]
## [,1] [,2] [,3] [,4]
## [1,] 7 15 23 31
## [2,] 10 22 34 46
##
## [[2]]
## [,1] [,2]
## [1,] 37 29
## [2,] 56 44
##
## [[3]]
## [1] "not possible"
##
## [[4]]
## [,1] [,2] [,3] [,4]
## [1,] 10 22 34 46
## [2,] 13 29 45 61
##
## [[5]]
## [,1] [,2]
## [1,] 56 44
## [2,] 75 59
##
## [[6]]
## [1] "not possible"
##
## [[7]]
## [,1] [,2] [,3] [,4]
## [1,] 11 23 35 47
## [2,] 14 30 46 62
## [3,] 17 37 57 77
## [4,] 20 44 68 92
##
## [[8]]
## [,1] [,2]
## [1,] 55 43
## [2,] 74 58
## [3,] 93 73
## [4,] 112 88
##
## [[9]]
## [1] "not possible"