Precision - Recall: Graphical Representation

I'm a little bit confused with precision recall. I read some papers about recommender systems, where in one paper they have a graphical representation and in other papers they don't (they just have the values for precision/recall). What is the advantage of a graphical representation?

Am I right, that for a graph you have to do something like a step function? e.g. you have a list of values true,true,false,true,false and you begin with the first one, calculate precision recall and then draw that point into the graph. For the next point, you take the first and the second value true,true into account, calculate precision recall, draw the point... and so on. Am I right that this is similar to drawing a ROC curve?