用 trycatch 循环一个向量

Question

我正在尝试对列表进行匹配，但我无法从我的函数中获得某种输出。循环在 vec[3] 处失败，这就是我使用 trycatch 的原因。但我仍然无法在我的函数输出中得到任何匹配。我无法输出任何东西。申请家庭也可以做同样的事情吗？

我试图在 vec 上匹配 loc。 vec[3] 将失败，因为我没有匹配。

vec=c('i am going to ooty corbett','i have to go to ooty', 'i have to go to manali')
loc=c('ooty','corbett')

out 是我试图为匹配构建的向量。

out=NULL
res_m=function(x,y){
    out[i]=tryCatch(
        {
            for(i in 1:length(y)){
                print(i)
                x=tolower(x)
                y=strsplit(y[i], " ")[[1]]
                out[i]=intersect(x,y)
            }
        },error=function(cond) {
            out[i]=NA
        },
        finally=print("can do")
    )    
    return(out[i])
}
res=res_m(loc,vec)

使用 ifelse，我得到了它的工作。但仍然可以从我的方法中找到解决方案。

res=NULL
out=NULL

for (i in 1:length(y)) {
    print(i)
    x = tolower(x)
    z = strsplit(y[i], " ")[[1]]
    out = intersect(x,z)
    if (length(out) == 0) {
        res[i] = NA
    }else{
        res[[i]] = out
    }
}

Answer 1

在您的res_m 中，您没有将“out”初始化为适当的对象，而且您正在覆盖“y”：

res_m = function(x, y)
{
    out = vector("list", length(y)) 
    for(i in 1:length(y)) {
        x = tolower(x)
        yy = strsplit(y[i], " ")[[1]]
        out[[i]] = intersect(x, yy)     
    }

    return(out)
}
res_m(loc, vec)
#[[1]]
#[1] "ooty"    "corbett"
#
#[[2]]
#[1] "ooty"
#
#[[3]]
#character(0)

您可以将tolower 和strsplit 移出循环：

res_m2 = function(x, y)
{
    out = vector("list", length(y))
    x = tolower(x)
    y = strsplit(y, " ")
    for(i in seq_along(y)) out[[i]] = intersect(x, y[[i]])
    return(out)
}
res_m2(loc, vec)
#[[1]]
#[1] "ooty"    "corbett"
#
#[[2]]
#[1] "ooty"
#
#[[3]]
#character(0)

或者使用lapply:

res_m3 = function(x, y)
{
    x = tolower(x)
    lapply(strsplit(y, " "), function(yy) intersect(x, yy))
}   
res_m3(loc, vec)
#[[1]]
#[1] "ooty"    "corbett"
#
#[[2]]
#[1] "ooty"
#
#[[3]]
#character(0)

如果你有犯了错误：

force_error = function(x, y)
{
    out = vector("list", length(y))
    x = tolower(x)
    y = strsplit(y, " ")
    for(i in seq_along(y)) 
        tryCatch(expr =  { out[i] = intersect(x, y[[i]]) }, 
                 error = function(e) { 
                     cat(sprintf("error in in 'i = %d'\n    --> %s\n", i, e))
                     out[i] <<- NA
                 }, 
                 warning = function(w) {
                     cat(sprintf("warning in in 'i = %d'\n    --> %s\n", i, w))
                     out[i] <<- NA
                 })
    return(out)
}   
force_error(loc, vec)
#warning in in 'i = 1'
#    --> simpleWarning in out[i] = intersect(x, y[[i]]): number of items to replace is not a multiple of replacement length
#
#error in in 'i = 3'
#    --> Error in out[i] = intersect(x, y[[i]]): replacement has length zero
#
#[[1]]
#[1] NA
#
#[[2]]
#[1] "ooty"
#
#[[3]]
#[1] NA

或者，您可以使用

regmatches(vec, gregexpr(paste(loc, collapse = "|"), vec))
#[[1]]
#[1] "ooty"    "corbett"
#
#[[2]]
#[1] "ooty"
#
#[[3]]
#character(0)