FCLoopAddEdgeTags[edges_List, labels_List] adds
user-defined styles and labels to the given edges using the provided
list of labels. Styles and labels are attached using the replacement
rules provided via the Style and Labeled
options.
If you use FCLoopIntegralToGraph for visualizing loop
integrals, the first two entries of its output can be used as the input
for FCLoopAddEdgeTags, e.g.
FCLoopAddEdgeTags[FCLoopIntegralToGraph[FAD[p, p - k], {p}][[1 ;; 2]]]
GraphPlot[%]\{-3\leftrightarrow 2,-1\leftrightarrow 1,1\leftrightarrow 2,1\leftrightarrow 2\}
If you just want to plot the obtained graph, it is easier to process
the output of FCLoopIntegralToGraph directly with
FCLoopGraphPlot, which internally uses
FCLoopAddEdgeTags.
FCLoopIntegralToGraph[FAD[p, p - k], {p}]
FCLoopGraphPlot[%]\left\{\{-3\to 2,-1\to 1,1\to 2,1\to 2\},\{k,k,\{p,1,0\},\{p-k,1,0\}\},\left\{0,0,\frac{1}{(p^2+i \eta )},\frac{1}{((p-k)^2+i \eta )}\right\},1\right\}
