如何将cat的输出分配给对象？

Question

如何在下面的例子中跳过写入文件"test.txt"的步骤,即将cat-result分配给一个对象,并仍然达到相同的最终结果？

我想我会包含完整的例子来说明问题的背景.

test <- c("V 1", "x", "1 2 3", "y", "3 5 8", "V 2", "x", "y", "V 3", "y", "7 2 1", "V 4", "x", "9 3 7", "y")

# Write selection to file
cat(test, "\n", file="test.txt")
test2 <- readLines("test.txt")
test3 <- strsplit(test2, "V ")[[1]][-1]

# Find results
x <- gsub("([0-9]) (?:x )?([0-9] [0-9] [0-9])?.*", "\\1 \\2 ", test3, perl = TRUE)
y <- gsub("([0-9]).* y ?([0-9] [0-9] [0-9])?.*", "\\1 \\2 ", test3, perl = TRUE)

# Eliminate tests with no results
x1 <- x[regexpr("[0-9] ([^0-9]).*", x) == -1]
y1 <- y[regexpr("[0-9] ([^0-9]).*", y) == -1]

# Dataframe of results
xdf1 <- read.table(textConnection(x1), col.names=c("id","x1","x2","x3"))
ydf1 <- read.table(textConnection(y1), col.names=c("id","y1","y2","y3"))
closeAllConnections()

# Dataframe of tests with no results
x2 <- x[regexpr("[0-9] ([^0-9]).*", x) == 1]
y2 <- y[regexpr("[0-9] ([^0-9]).*", y) == 1]

df1 <- as.integer(x2[x2 == y2])
df1 <- data.frame(id = df1)

# Merge dataframes
results <- merge(xdf1, ydf1, all = TRUE)
results <- merge(results, df1, all = TRUE)
results

结果是:

  id x1 x2 x3 y1 y2 y3
1  1  1  2  3  3  5  8
2  2 NA NA NA NA NA NA
3  3 NA NA NA  7  2  1
4  4  9  3  7 NA NA NA

Answer 1

作为更通用的解决方案,您可以使用捕获输出功能.它产生一个字符向量,其元素对应于输出的每一行.

你的例子:

test2<-capture.output(cat(test))

这是一个多行示例:

> out<-capture.output(summary(lm(hwy~cyl*drv,data=mpg)))
> out
 [1] ""                                                               
 [2] "Call:"                                                          
 [3] "lm(formula = hwy ~ cyl * drv, data = mpg)"                      
 [4] ""                                                               
 [5] "Residuals:"                                                     
 [6] "    Min      1Q  Median      3Q     Max "                       
 [7] "-8.3315 -1.4139 -0.1382  1.6479 13.5861 "                       
 [8] ""                                                               
 [9] "Coefficients:"                                                  
[10] "            Estimate Std. Error t value Pr(>|t|)    "           
[11] "(Intercept)  32.1776     1.2410  25.930  < 2e-16 ***"           
[12] "cyl          -2.0049     0.1859 -10.788  < 2e-16 ***"           
[13] "drvf          8.4009     1.8965   4.430 1.47e-05 ***"           
[14] "drvr          8.2509     6.4243   1.284    0.200    "           
[15] "cyl:drvf     -0.5362     0.3422  -1.567    0.119    "           
[16] "cyl:drvr     -0.5248     0.8379  -0.626    0.532    "           
[17] "---"                                                            
[18] "Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 "
[19] ""                                                               
[20] "Residual standard error: 2.995 on 228 degrees of freedom"       
[21] "Multiple R-squared: 0.7524,\tAdjusted R-squared: 0.747 "         
[22] "F-statistic: 138.6 on 5 and 228 DF,  p-value: < 2.2e-16 "       
[23] ""    

Answer 2

取而代之的cat荷兰国际集团到一个文件,为什么不使用paste命令生成的字符串呢？

> paste(test, collapse="\n")
[1] "V 1\nx\n1 2 3\ny\n3 5 8\nV 2\nx\ny\nV 3\ny\n7 2 1\nV 4\nx\n9 3 7\ny"

现在不是做cat那么readlines你可以直接通过这串入strsplit.