title: R scatterplot3d: a custom axis step and ticks
body: <p>Greeting to all.</p>
  
  <p>I am striving with a <code>scatterplot3d</code> plot -- a graphical representation of a data.frame of three variables where one of them is a response variable, where I have a wrong representation of the axis steps. Here is the code ("temp" is a data.frame):</p>
  
  <pre><code>library(scatterplot3d)
  temp[,1] &lt;- as.numeric(levels(temp[,1]))[temp[,1]]
  
  for (m in temp[,2])  m &lt;-  as.factor(as.numeric(m))
  
  for (m in temp[,3])  m &lt;-  as.factor(as.numeric(m))
  
  colnames(temp) = c("Values", "Factors", "AntiFactors") # "Values" is that responce variable
  xtickmarks&lt;-c("AntiFactor1","AntiFactor1", "AntiFactor3")
  ytickmarks&lt;-c("Factor1","Factor2")
  
  plot3d &lt;- scatterplot3d(temp[,3], temp[,2], temp[,1], color = "blue",
                          pch = 19, type = "h", box = T, xaxt = "n", 
                          x.ticklabs=xtickmarks, y.ticklabs=ytickmarks,
                          zlab = "Time, min.")
  
  dput(temp)
  
  structure(list(Values = c(395, 310, 235, 290, 240, 490, 270, 
  225, 430, 385, 170, 55, 295, 320, 270, 130, 300, 285, 130, 200, 
  225, 90, 205, 340, 3, 8, 1, 0, 0, 0, 3, 2, 5, 2, 3, 5, 2, 3, 
  200, 5, 5, 10, 5, 5, 5, 10, 10, 130, 5, 200, 80, 10, 360, 10, 
  5, 8, 30, 8, 10, 10, 10, 5, 240, 120, 3, 10, 25, 5, 5, 10, 190, 
  30, 115, 1, 1, 1, 2, 3, 5, 2, 5, 3, 3, 3, 2, 3, 2, 3, 0, 0, 195, 
  150, 2, 2, 0, 2, 1, 1, 2, 1, 2, 1, 1, 1, 3, 2, 2, 1, 2, 2, 1, 
  1, 2, 3, 2, 2, 1, 3, 1, 1), Factors = structure(c(1L, 1L, 1L, 
  1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
  1L, 1L, 1L, 1L, 1L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
  1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
  1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L), .Label = c("Factor1", "Factor2"), class = "factor"), 
      AntiFactors = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
      1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
      1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
      2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
      2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
      2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
      3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
      3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
      3L, 3L, 3L, 3L, 3L, 3L, 3L), .Label = c("AntiFactor1", "AntiFactor2", 
      "AntiFactor3"), class = "factor")), .Names = c("Values", 
  "Factors", "AntiFactors"), row.names = c(NA, -120L), class = "data.frame")
  </code></pre>
  
  <p>Here is the picture of that plot I got:
  <img src="https://i.stack.imgur.com/tDFCL.jpg" alt="enter image description here"></p>
  
  <p>The trouble is what I got twice more ticks at the x and y axis than it is needed. It is intended to have just one set of those Factor1..2 and AntiFactor1..3 ticks at each of those x, y axis. If I run that <code>scatterplot3d</code> without using <code>x.ticklabs</code> option, it gives "0, 0.5, 1, 1.5, 2.0, ...3.0" ticks etc at the axis. What is the way to set my step in x, y axis to be just a strong integer "1", so that all my discrete ticks to be displayed in their right place?</p>