使用向量中的最后一个非空值填充空值

Question

我想在一个带有前面值的向量中填入缺失值(不是NA,只是''!).例如,如果我将矢量定义为

vec <- c('Titanic', '', '', '', 'Donnie Darko', '', '', 'Twin Peaks', 
         'American Hustle', '')

我的输出矢量将是

'Titanic', 'Titanic', 'Titanic', 'Titanic', 'Donnie Darko', 'Donnie Darko', 
'Donnie Darko', 'Twin Peaks', 'American Hustle', 'American Hustle'

我怎样才能做到这一点？

Answer 1

这是一个双线nzchar和子集,应该非常有效.

# get logical vector of elements with non-empty character elements
notMissings <- nzchar(movies)
# fill in missing values
movies[notMissings][cumsum(notMissings)]
 [1] "Titanic"         "Titanic"         "Titanic"         "Titanic"        
 [5] "Donnie Darko"    "Donnie Darko"    "Donnie Darko"    "Twin Peaks"     
 [9] "American Hustle" "American Hustle"

这是第二种使用方法rle.

# get run length encodings
temp <- rle(movies)
# get missing values    
missings <- nchar(temp$values) == 0
# fill in missing values
temp$values[missings] <- temp$values[which(missings) - 1]

# expand
inverse.rle(temp)
 [1] "Titanic"         "Titanic"         "Titanic"         "Titanic"        
 [5] "Donnie Darko"    "Donnie Darko"    "Donnie Darko"    "Twin Peaks"     
 [9] "American Hustle" "American Hustle"

请注意,如果第一个元素是空字符'',则第二个方法将抛出错误.

数据

movies <- c('Titanic', '', '', '', 'Donnie Darko', '', '', 'Twin Peaks',
            'American Hustle', '')