fixed hidden dependency

vignettes/gsoc_2017_additions.Rmd

@@ -255,7 +255,7 @@ The probabilities we get are with an error of $10^{-3}$
 
 # Continuous time markovchain generator using frequency Matrix
 
-The package provides `freq2Generator` function. It takes in a matrix representing relative frequency values along with time taken to provide a continuous time markovchain generator matrix. Here, frequency matrix is a 2-D matrix of dimensions equal to relative number of possible states describing the number of transitions from a state $i$ to $j$ in time $t$, which is another parameter to be provided to the function. The function also allows to chose among three methods for calculation of the generator matrix.[@freqArticle]
+The package provides `freq2Generator` function. It takes in a matrix representing relative frequency values along with time taken to provide a continuous time markovchain generator matrix. Here, frequency matrix is a 2-D matrix of dimensions equal to relative number of possible states describing the number of transitions from a state $i$ to $j$ in time $t$, which is another parameter to be provided to the function. The function also allows to chose among three methods for calculation of the generator matrix [@freqArticle]. It requires the [@pkg:ctmcd] package.
 
 Three methods are as follows:
 
@@ -268,9 +268,11 @@ See reference for details about the methods.
 
 Here is an example matrix on which `freq2Generator` function is run:
 ``` {r}
+if(requireNamespace(package='ctmcd', quietly = TRUE)) {
 sample <- matrix(c(150,2,1,1,1,200,2,1,2,1,175,1,1,1,1,150),nrow = 4,byrow = TRUE)
 sample_rel = rbind((sample/rowSums(sample))[1:dim(sample)[1]-1,],c(rep(0,dim(sample)[1]-1),1)) 
 freq2Generator(sample_rel,1)
+}
 ```