title: Nbclust throwing error
body: <p>I am trying to run a dataframe of 9 columns and 1064 rows through a k-means clustering algorithm, but I get the following error:</p>
  
  <p><code>Error in NbClust(df, min.nc = 2, max.nc = 15, method = "kmeans") : 
    The TSS matrix is indefinite. There must be too many missing values. The index cannot be calculated.</code></p>
  
  <p>However, there are no missing values </p>
  
  <pre><code>&gt; dim(df)
  [1] 1064    9
  
  &gt; sum(is.na(df))
  [1] 0
  </code></pre>
  
  <p>Any idea what the problem could be and how to resolve it? </p>
  
  <pre><code>&gt; head(df)
    hr_830 hr_930 hr_1030 hr_1130 hr_160 hr_180 hr_190 hr_200 hr_0
  1      2      2       2       2      2      2      2      2    2
  2      2      2       2       2      2      2      2      2    3
  3      2      2       2       2      2      2      2      2    3
  4      2      2       2       2      2      2      2      2    2
  5      2      2       2       2      2      2      2      2    2
  6      2      2       2       2      2      2      2      2    4
  </code></pre>
  
  <p>here is a sample of the input:</p>
  
  <pre><code>  &gt; dput(input)
  structure(list(hr_830 = c(2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 4L, 
  2L, 4L, 4L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L
  ), hr_930 = c(2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 4L, 2L, 4L, 4L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), hr_1030 = c(2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 4L, 2L, 4L, 4L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), hr_1130 = c(2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 4L, 4L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L), hr_160 = c(2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 4L, 4L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L), hr_180 = c(2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 4L, 2L, 4L, 4L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), hr_190 = c(2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 4L, 2L, 4L, 4L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), hr_200 = c(2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 4L, 2L, 4L, 4L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L), hr_0 = c(2L, 3L, 3L, 2L, 2L, 4L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 4L, 2L, 2L, 2L, 2L, 2L, 2L
  )), .Names = c("hr_830", "hr_930", "hr_1030", "hr_1130", "hr_160", 
  "hr_180", "hr_190", "hr_200", "hr_0"), row.names = c(NA, 25L), class = "data.frame")
  </code></pre>