title: predict svm in R returns different results with the same imput
body: <p>I am using SVM with a very simple example, but the results returned by the predict method are not always the same. </p>
  
  <p>Here is the code I run: </p>
  
  <pre><code>library(e1071)
  </code></pre>
  
  <p>## don't do:  r_m(list=ls())</p>
  
  <pre><code>x =  c(2,3,3,1,1,2,3  ,   1,1,2,2,3,2,3)
  dim(x) &lt;- c(7 ,2)   
  y = factor(c(T,T,T,F,F,F,F))
  
  DF &lt;- data.frame(x = x, y = y)
  model = svm(y ~ x, data = DF,  method = "C-classification", cost = 1, 
               kernel = "linear")
  
  # exactly the same data as x
  xtest =     c(2,3,3,1,1,2,3  ,   1,1,2,2,3,2,3) 
  dim(xtest) &lt;- c(7 ,2)  
  
  predict(model,  newdata = data.frame(x = xtest), prob=TRUE)  
  predict(model,  newdata = data.frame(x = xtest),  prob=TRUE)  
  predict(model,  newdata = data.frame(x = xtest),  prob=TRUE)  
  </code></pre>
  
  <p>But I have the following output:</p>
  
  <pre><code>&gt; predict(model,  newdata = data.frame(x = xtest), prob=TRUE)  
     1    2    3    4    5    6    7 
  TRUE TRUE TRUE TRUE TRUE TRUE TRUE 
  attr(,"probabilities")
    TRUE FALSE
  1  0.5   0.5
  2  0.5   0.5
  3  0.5   0.5
  4  0.5   0.5
  5  0.5   0.5
  6  0.5   0.5
  7  0.5   0.5
  Levels: FALSE TRUE
  &gt; predict(model,  newdata = data.frame(x = xtest),  prob=TRUE)  
     1    2    3    4    5    6    7 
  TRUE TRUE TRUE TRUE TRUE TRUE TRUE 
  attr(,"probabilities")
    TRUE FALSE
  1  0.5   0.5
  2  0.5   0.5
  3  0.5   0.5
  4  0.5   0.5
  5  0.5   0.5
  6  0.5   0.5
  7  0.5   0.5
  Levels: FALSE TRUE
  &gt; predict(model,  newdata = data.frame(x = xtest),  prob=TRUE)
      1     2     3     4     5     6     7 
  FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
  attr(,"probabilities")
            TRUE FALSE
  1 3.000001e-14     1
  2 3.000001e-14     1
  3 3.000001e-14     1
  4 3.000001e-14     1
  5 3.000001e-14     1
  6 3.000001e-14     1
  7 3.000001e-14     1
  Levels: FALSE TRUE
  </code></pre>
  
  <p>Sometimes it displays the same output 3 times in a row, but sometimes it displays something different as you can see above.</p>
  
  <p>Note: I am using RStudio</p>
  
  <p>Why does it happen? 
  Why does the predict method never predicts something coherent?  </p>