Running examples in 'ggnetwork-Ex.R' failed
The error most likely occurred in:

> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: fortify.network
> ### Title: Fortify method for networks of class 'network'
> ### Aliases: fortify.network
> 
> ### ** Examples
> 
> if (require(ggplot2) && require(network)) {
+ 
+   # source: ?network::flo
+   data(flo)
+ 
+   # data example
+   ggnetwork(flo)
+ 
+   # plot example
+   ggplot(ggnetwork(flo), aes(x, y, xend = xend, yend = yend)) +
+     geom_edges(alpha = 0.5) +
+     geom_nodes(size = 12, color = "white") +
+     geom_nodetext(aes(label = vertex.names), fontface = "bold") +
+     theme_blank()
+ 
+   # source: ?network::emon
+   data(emon)
+ 
+   # data example
+   ggnetwork(emon[[1]], layout = "target", niter = 100)
+ 
+   # data example with edge weights
+   ggnetwork(emon[[1]], layout = "kamadakawai", weights = "Frequency")
+ 
+   # plot example with straight edges
+   ggplot(ggnetwork(emon[[1]], layout = "kamadakawai", arrow.gap = 0.025),
+          aes(x, y, xend = xend, yend = yend)) +
+     geom_edges(aes(color = Frequency),
+                arrow = arrow(length = unit(10, "pt"), type = "closed")) +
+     geom_nodes(aes(size = Formalization)) +
+     scale_color_gradient(low = "grey50", high = "tomato") +
+     scale_size_area(breaks = 1:3) +
+     theme_blank()
+ 
+   # plot example with curved edges
+   ggplot(ggnetwork(emon[[1]], layout = "kamadakawai", arrow.gap = 0.025),
+          aes(x, y, xend = xend, yend = yend)) +
+     geom_edges(aes(color = Frequency), curvature = 0.1,
+                arrow = arrow(length = unit(10, "pt"), type = "open")) +
+     geom_nodes(aes(size = Formalization)) +
+     scale_color_gradient(low = "grey50", high = "tomato") +
+     scale_size_area(breaks = 1:3) +
+     theme_blank()
+ 
+   # facet by edge attribute
+   ggplot(ggnetwork(emon[[1]], arrow.gap = 0.02, by = "Frequency"),
+          aes(x, y, xend = xend, yend = yend)) +
+     geom_edges(arrow = arrow(length = unit(5, "pt"), type = "closed")) +
+     geom_nodes() +
+     theme_blank() +
+     facet_grid(. ~ Frequency, labeller = label_both)
+ 
+   # user-provided layout
+   ggplot(ggnetwork(emon[[1]], layout = matrix(runif(28), ncol = 2)),
+          aes(x, y, xend = xend, yend = yend)) +
+     geom_edges(arrow = arrow(length = unit(5, "pt"), type = "closed")) +
+     geom_nodes() +
+     theme_blank()
+ 
+ }
Loading required package: network
network: Classes for Relational Data
Version 1.16.0 created on 2019-11-30.
copyright (c) 2005, Carter T. Butts, University of California-Irvine
                    Mark S. Handcock, University of California -- Los Angeles
                    David R. Hunter, Penn State University
                    Martina Morris, University of Washington
                    Skye Bender-deMoll, University of Washington
 For citation information, type citation("network").
 Type help("network-package") to get started.

 ----------- FAILURE REPORT -------------- 
 --- failure: the condition has length > 1 ---
 --- srcref --- 
: 
 --- package (from environment) --- 
ggnetwork
 --- call from context --- 
ggnetwork(flo)
 --- call from argument --- 
if (class(x) == "igraph") {
    fortify.igraph(x, ...)
} else {
    if (!network::is.network(x)) {
        x = try(network::network(x), silent = TRUE)
    }
    if (!network::is.network(x)) {
        stop("could not coerce object to a network")
    }
    else {
        fortify.network(x, ...)
    }
}
 --- R stacktrace ---
where 1: ggnetwork(flo)

 --- value of length: 2 type: logical ---
[1] FALSE FALSE
 --- function from context --- 
function (x, ...) 
{
    if (class(x) == "igraph") {
        fortify.igraph(x, ...)
    }
    else {
        if (!network::is.network(x)) {
            x = try(network::network(x), silent = TRUE)
        }
        if (!network::is.network(x)) {
            stop("could not coerce object to a network")
        }
        else {
            fortify.network(x, ...)
        }
    }
}
<bytecode: 0x46e06f8>
<environment: namespace:ggnetwork>
 --- function search by body ---
Function ggnetwork in namespace ggnetwork has this body.
 ----------- END OF FAILURE REPORT -------------- 
Error in if (class(x) == "igraph") { : the condition has length > 1
Calls: ggnetwork
Execution halted