| title | author | license | tags | summary | layout | src |
|---|---|---|---|---|---|---|
Using Sugar Function any() |
Ross Bennett |
GPL (>= 2) |
sugar |
Illustrates the use of sugar function any() |
post |
2012-12-23-sugar-any.cpp |
The sugar function any() answers the question, "Are any of the values ... ?".
The any_sug() function takes a LogicalVector as an argument and allows one to enter an expression for the argument as shown in the R examples. In this example, it is simply wrapper around the sugar function any() and includes is_true to return a boolean.
Note that when comparing two vectors, it is an element-wise comparison.
(i.e. x[0] > y[0], ..., x[n] > y[n])
{% highlight cpp %} #include <Rcpp.h> using namespace Rcpp;
// [[Rcpp::export]] bool any_sug(LogicalVector x){ // Note the use of is_true to return a bool type return is_true(any(x == TRUE)); } {% endhighlight %}
{% highlight r %} x <- c(3, 9, 0, 2, 7, -1, 6) y <- c(8, 3, 2, 6, 1, 5, 0) any_sug(x < 10) {% endhighlight %}
[1] TRUE
{% highlight r %} any_sug(x != 3) {% endhighlight %}
[1] TRUE
{% highlight r %} any_sug(x >= y) {% endhighlight %}
[1] TRUE
{% highlight r %} any_sug(y == 0) {% endhighlight %}
[1] TRUE
While the above function may seem trivial, it can be easy to forget is_true() when using any() and will result in a compile error. The check_negative() function below is an example of a simple utility function to check if a vector contains negative values using the any_sug() function defined above.
{% highlight cpp %} // [[Rcpp::export]] void check_negative(NumericVector x) { if(any_sug(x < 0)) { Rcout << "The vector contains negative numbers" << std::endl; // do something } else { Rcout << "The vector does not contain negative numbers" << std::endl; // do something else } } {% endhighlight %}
{% highlight r %} check_negative(x) {% endhighlight %}
The vector contains negative numbers
{% highlight r %} check_negative(y) {% endhighlight %}
The vector does not contain negative numbers