r - ループを使用せずに、ゼロ以外のエントリが 4 つ未満の行を削除する

Question

データセットは次のようになります。

"1" 10 40 "r" "q" "0" "r" "r" "0" "r" "0" "0" "0" "0" "0" "t" "q" "0" "0" "s" "0" "r" 0 "0" 0 "0" "0" 0 0 0 "0"
"2" 10 173 "s" "s" "s" "0" "0" "s" "s" "0" "t" "t" "s" "t" "t" "r" "s" "0" "q" "0" "0" 0 "0" 0 "0" "0" 0 0 0 "0"
"3" 10 2107 "t" "0" "0" "s" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" 0 "0" 0 "0" "0" 0 0 0 "0"
"4" 10 993 "s" "0" "q" "s" "s" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" 0 "0" 0 "0" "0" 0 0 0 "0"
"5" 10 1712 "t" "0" "s" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "s" "0" "t" "0" 0 "0" 0 "0" "0" 0 0 0 "0"
"6" 776 1872 "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" 0 "r" 0 "0" "0" 0 0 0 "s"

出力は次のようになります。

"1" 10 40 "r" "q" "0" "r" "r" "0" "r" "0" "0" "0" "0" "0" "t" "q" "0" "0" "s" "0" "r" 0 "0" 0 "0" "0" 0 0 0 "0"
"2" 10 173 "s" "s" "s" "0" "0" "s" "s" "0" "t" "t" "s" "t" "t" "r" "s" "0" "q" "0" "0" 0 "0" 0 "0" "0" 0 0 0 "0"
"4" 10 993 "s" "0" "q" "s" "s" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" 0 "0" 0 "0" "0" 0 0 0 "0"
"5" 10 1712 "t" "0" "s" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "0" "s" "0" "t" "0" 0 "0" 0 "0" "0" 0 0 0 "0"

私が試したコードは次のとおりです。

x=read.table("sample.txt")
nrowx=nrow(x) 
for(i in 1:nrowx)
{
    count=0
    for(j in 3:30)
    {
        if(x[i,j]!=0)
        count = count+1
    }   
    if(count<4)
    x[i,]=NA    
}  
x=x[complete.cases(x),]

ループを含まない方法を提案してください。