R函数在tibble中打印列和行 - 我做错了什么？

Question

我创建了一个函数来打印 tibble 的指定列块和行块，它大部分工作得很好。有一个我想不通的小问题。当我有一个较小的数据集并想要打印所有列（在指定的行范围内）时，如果我将列数指定为参数，则不会打印任何内容。但是，如果我指定少一列，它会打印但在控制台中分成两组行。在这种情况下，我希望能够在一行中查看所有数据。

我的函数和一些测试数据如下：

# Need to specify:
# 1.Dataframe name
# 2.Number of cols to print in a block
# 3.Start row
# 4.End row
  print_cols <- function(df, ncols, rowstart, rowend) {
    numcols <- length(df)
    i <- 1
    while (i + (ncols-1) < numcols) {
      cat("\n")
      print(paste0("Columns ", i, " to ", (i + (ncols-1)), ": Rows ", rowstart, " to ", rowend))
      print(df[rowstart:rowend, i:(i + (ncols-1))], n = Inf)
      i <- i + ncols
      if (i + (ncols-1) >= numcols) {
        cat("\n")
        print(paste0("Columns ", i, " to ", numcols, ": Rows ", rowstart, " to ", rowend))
        print(df[rowstart:rowend, i:numcols], n = Inf)
      }
    }
  }

# Simulate data and test function
# Print blocks of cols (when many variables)  
dat <- rep(rnorm(50, 50, 20), 100)
dat <- as_tibble(matrix(data = dat, nrow = 50, ncol = 100, byrow = F))
print_cols(dat, 20, 20, 40) # works fine

# Print all columns (when only a few variables)
dat2 <- rep(rnorm(50, 50, 20), 10)
dat2 <- as_tibble(matrix(data = dat2, nrow = 50, ncol = 10, byrow = F))
print_cols(dat2, 10, 20, 40) # prints nothing - WHY??
print_cols(dat2, 9, 20, 40) # need to specify one column less in order to print```

Answer 1

以下是我将如何重写您的函数：

print_cols = function(df, ncols, rowstart, rowend) {
  if(!is_tibble(df)) {df = as_tibble(df)}
  col_starts = seq(from = 1, to = ncol(df), by = ncols)
  for(i in col_starts) {
    cat("\n")
    if(i < tail(col_starts, 1)) {
      cols = i + 0:(ncols - 1) 
    } else { ## last iteration
      cols = i:ncol(df)
    }
    message(sprintf(
        "Columns %s to %s: Rows %s to %s",
        cols[1], tail(cols, 1),
        rowstart, rowend
    ))
    print(df[rowstart:rowend, cols], n = Inf)
  }
}

print_cols(mtcars, 8, 2, 3)
# Columns 1 to 8: Rows 2 to 3
# # A tibble: 2 × 8
#     mpg   cyl  disp    hp  drat    wt  qsec    vs
#   <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
# 1  21       6   160   110  3.9   2.88  17.0     0
# 2  22.8     4   108    93  3.85  2.32  18.6     1
# 
# Columns 9 to 11: Rows 2 to 3
# # A tibble: 2 × 3
#      am  gear  carb
#   <dbl> <dbl> <dbl>
# 1     1     4     4
# 2     1     4     1

R函数在tibble中打印列和行 - 我做错了什么？

R Function to print columns and rows in tibble - what am I doing wrong?

r

function