r: NbClust() only computes 26 out of 30 indices - "Gap", "Gamma", "Gplus" and "Tau" are missing
<p>I am calling <code>NbClust()</code> on my <code>df</code> containing four columns of numerical, scaled, "NON-NA" data. My code looks as follows</p>

<pre><code>nc = NbClust(scale(df),distance="euclidean", min.nc=2, max.nc=7,method="complete")
</code></pre>

<p>In the description of <code>?NbClust()</code> it is said that it computes 30 different indices for the data but in my case it only computes 26 and leaves out the following four:</p>

<ul>
<li>Gap-Index</li>
<li>Gamma-Index</li>
<li>Gplus-Index</li>
<li>Tau-Index</li>
</ul>

<p>Does anyone know why it does not compute them? I am happy for any advice, hint!</p>

<p>Data looks like this</p>

<pre><code>df = structure(list(Birthrate = c(18.2, 8.5, 54.1, 1.4, 2.1, 83.6, 
17, 1, 0.8, 61.7, 4.9, 7.9, 2, 14.2, 48.2, 17.1, 10.4, 37.5, 
1.6, 49.5, 10.8, 6.2, 7.1, 7.8, 3, 3.7, 4.2, 8.7), GDP = c(1.22, 
0.06, 0, 0.54, 2.34, 0.74, 1.03, 1.21, 0, 0.2, 1.41, 0.79, 2.75, 
0.03, 11.13, 0.05, 2.99, 0.71, 0, 0.9, 1.15, 0, 1.15, 1.44, 0, 
0.71, 1.21, 1.45), Income = c(11.56, 146.75, 167.23, 7, 7, 7, 
10.07, 7, 7, 7, 47.43, 20.42, 7.52, 7, 7, 15.98, 15.15, 20.42, 
7, 22.6, 7, 7, 18.55, 7, 7.7, 7, 7, 7), Population = c(54, 94, 
37, 95, 98, 31, 78, 97, 95, 74, 74, 81, 95, 16, 44, 63, 95, 20, 
95, 83, 98, 98, 84, 62, 98, 98, 97, 98)), .Names = c("Birthrate", 
"GDP", "Income", "Population"), class = "data.frame", row.names = c(NA, 
-28L))
</code></pre>