title: R "increasing 'x' and 'y' values expected
body: <p>I'm trying to create a perspective graph in R and keep getting the increasing 'x' and 'y' error. I've tried numerous options but I can't seem to figure this out. Any help would be appreciated!</p>
  
  <pre><code>fit.A &lt;- data.frame(Temp.f="Ambient",x,y)
  fit.A$pred &lt;- predict(model=lrNH4,newdata=fit.A)
  
  x
   [1] 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
  [17] 0.619 0.626 0.630 0.635 0.649 0.656 1.902 1.947 1.967 2.056 2.689 2.707 2.758 2.760 2.943 2.978
  [33] 2.992 3.020 4.564 4.854 5.893 6.029 6.051 6.067
  
  y
   [1] 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
  [17] 0.479 0.530 0.566 0.605 0.635 0.726 1.909 1.916 2.128 2.195 2.636 2.645 2.747 2.777 2.943 3.057
  [33] 3.169 3.203 4.657 4.813 5.956 5.986 6.154 6.157
  
  persp(x,y,z=matrix(fit.A$pred,nrow=length(x),ncol=length(y),byrow=TRUE),
  zlim=c(140,700))
  </code></pre>
  
  <blockquote>
    <p>Error in persp.default(x, y, z = matrix(fit.A$pred, nrow = length(x), 
    :    increasing 'x' and 'y' values expected</p>
  </blockquote>