title: summarize_at for multiple variables and multiple functions with different arguments in R?
body: <p>I have 5 variables in my df, I want to summarize_at them using the following pattern for each variable:</p>
  
  <pre><code>min, quantile(.25), median, mean, qunatile(.75), max, sd
  </code></pre>
  
  <p>Here is my sample df, please advise how to do this:</p>
  
  <pre><code>df &lt;- structure(list(user_id = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
  1L), obs_id = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), scroll_id = c(3L, 
  3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), timestamp = c(1540202430007839232, 
  1540202430009840640, 1540202430010982656, 1540202430010982656, 
  1540202430011841792, 1540202430013843200, 1540202430015844608, 
  1540202430017846016, 1540202430019847168, 1540202430020992512
  ), start_time = c(1540202430007839232, 1540202430007839232, 1540202430007839232, 
  1540202430007839232, 1540202430007839232, 1540202430007839232, 
  1540202430007839232, 1540202430007839232, 1540202430007839232, 
  1540202430007839232), end_time = c(1540202430075907328, 1540202430075907328, 
  1540202430075907328, 1540202430075907328, 1540202430075907328, 
  1540202430075907328, 1540202430075907328, 1540202430075907328, 
  1540202430075907328, 1540202430075907328), gra_x = c(0.028428223, 
  0.028428223, 0.024191462, 0.024191462, 0.024191462, 0.024191462, 
  0.024191462, 0.024191462, 0.024191462, 0.008488427), gra_y = c(3.3407776, 
  3.3407776, 3.329257, 3.329257, 3.329257, 3.329257, 3.329257, 
  3.329257, 3.329257, 3.2995365), gra_z = c(9.220019, 9.220019, 
  9.224198, 9.224198, 9.224198, 9.224198, 9.224198, 9.224198, 9.224198, 
  9.234899), lin_acc_mag = c(1.87035263799625, 1.87035263799625, 
  1.87035263799625, 1.46659090346921, 1.46659090346921, 1.46659090346921, 
  1.46659090346921, 1.46659090346921, 1.46659090346921, 1.46659090346921
  ), vel_ang_unc_mag = c(0.363288181726866, 0.397720202371128, 
  0.397720202371128, 0.397720202371128, 0.462731530212917, 0.493683807731099, 
  0.553539962506893, 0.607457519129218, 0.629400228979264, 0.629400228979264
  )), .Names = c("user_id", "obs_id", "scroll_id", "timestamp", 
  "start_time", "end_time", "gra_x", "gra_y", "gra_z", "lin_acc_mag", 
  "vel_ang_unc_mag"), row.names = c(NA, -10L), class = c("grouped_df", 
  "tbl_df", "tbl", "data.frame"), vars = c("user_id", "obs_id", 
  "scroll_id"), drop = TRUE, indices = list(0:9), group_sizes = 10L, biggest_group_size = 10L, labels = structure(list(
      user_id = 1L, obs_id = 1L, scroll_id = 3L), row.names = c(NA, 
  -1L), class = "data.frame", vars = c("user_id", "obs_id", "scroll_id"
  ), drop = TRUE, .Names = c("user_id", "obs_id", "scroll_id")))
  
  
  df %&gt;% 
  summarize_at(vars(gra_x, gra_y, gra_z, lin_acc_mag, vel_ang_unc_mag), 
               funs(min, max, mean, median, sd, quantile, probs = c(0.25, 0.75)))  
  </code></pre>
  
  <p>Returns an error:</p>
  
  <blockquote>
    <p>Error in summarise_impl(.data, dots) : Column <code>gra_x_quantile</code> must be
    length 1 (a summary value), not 5</p>
  </blockquote>