blocks|key|279284|text|这里有两种方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|279285|设置绘图|279286|library(ggplot2)+
library(grid)
library(gridExtra)+

my_hist+<-+ggplot(diamonds,+aes(clarity,+fill+=+cut))+%2B+
++++geom_bar()+|code-block|syntax|javascript|279287|Cowplot方法|279288|#+Using+the+cowplot+package
legend+<-+cowplot::get_legend(my_hist)

grid.newpage()
grid.draw(legend)|279289|​|279290|📷|atomic|offset|length|279291|279292|自主开发的方法|279293|不知羞耻地窃取自：Inserting+a+table+under+the+legend+in+a+ggplot2+histogram|279294|##+Function+to+extract+legend
g_legend+<-+function(a.gplot){+
++++tmp+<-+ggplot_gtable(ggplot_build(a.gplot))+
++++leg+<-+which(sapply(tmp$grobs,+function(x)+x$name)+==+"guide-box")+
++++legend+<-+tmp$grobs[[leg]]+
++++legend
}+

legend+<-+g_legend(my_hist)+

grid.newpage()
grid.draw(legend)+|279295|由reprex+package创建于2018-05-31+(v0.2.0)。|279296|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/7ed3172162c0406ef664d86dedf2e0b8.png|imageAlt|1|LINK|MUTABLE|url|https://stackoverflow.com/questions/11883844/inserting-a-table-under-the-legend-in-a-ggplot2-histogram|2|http://reprex.tidyverse.org/^0|0|0|0|0|0|0|0|1|0|0|0|0|9|1L|1|0|0|1|E|2|0^^$0|@$1|2|3|4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1J|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1K|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|1L|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|1M|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|1N|8|@]|9|@]|A|$]]|$1|O|3|P|5|Q|7|1O|8|@]|9|@$R|1P|S|1Q|1|1R]]|A|$]]|$1|T|3|N|5|6|7|1S|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1T|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1U|8|@]|9|@$R|1V|S|1W|1|1X]]|A|$]]|$1|Y|3|Z|5|F|7|1Y|8|@]|9|@]|A|$G|H]]|$1|10|3|11|5|6|7|1Z|8|@]|9|@$R|20|S|21|1|22]]|A|$]]|$1|12|3|-4|5|6|7|23|8|@]|9|@]|A|$]]]|13|$14|$5|15|16|17|A|$18|19|1A|-4]]|1B|$5|1C|16|1D|A|$1E|1F]]|1G|$5|1C|16|1D|A|$1E|1H]]]]

<p>Here are 2 approaches:</p>

<h2>Set Up Plot</h2>



<pre class="lang-r prettyprint-override"><code>library(ggplot2) 
library(grid)
library(gridExtra) 

my_hist &lt;- ggplot(diamonds, aes(clarity, fill = cut)) + 
    geom_bar() 
</code></pre>

<h2>Cowplot approach</h2>

<pre class="lang-r prettyprint-override"><code># Using the cowplot package
legend &lt;- cowplot::get_legend(my_hist)

grid.newpage()
grid.draw(legend)
</code></pre>

<p><img src="https://i.imgur.com/MKXIGTB.png" alt=""></p>

<h2>Home grown approach</h2>

<p>Shamelessly stolen from: <a href="https://stackoverflow.com/questions/11883844/inserting-a-table-under-the-legend-in-a-ggplot2-histogram">Inserting a table under the legend in a ggplot2 histogram</a></p>

<pre class="lang-r prettyprint-override"><code>## Function to extract legend
g_legend &lt;- function(a.gplot){ 
    tmp &lt;- ggplot_gtable(ggplot_build(a.gplot)) 
    leg &lt;- which(sapply(tmp$grobs, function(x) x$name) == "guide-box") 
    legend &lt;- tmp$grobs[[leg]] 
    legend
} 

legend &lt;- g_legend(my_hist) 

grid.newpage()
grid.draw(legend) 
</code></pre>

<p>Created on 2018-05-31 by the <a href="http://reprex.tidyverse.org" rel="noreferrer">reprex package</a> (v0.2.0).</p>


blocks|key|279346|text|我正在对图中的顶点进行颜色编码，并希望尽可能简单、优雅和快速地生成一个图例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|279347|我认为最快的方法是先使用ggplot2单独生成图例，然后再使用viewport和layout()将图例粘贴到与igraph相同的图中|offset|length|style|CODE|279348|在此方法中，不需要在plot.igraph()函数中调用rescale或asp参数。|279349|在data.frame+leg上使用g_legend函数，其中有2列，x是适当的顶点属性，y是我的曲线图中使用的十六进制颜色代码，我完成了以下工作。|279350|我的签名对象是t8g|279351|legend+<-+g_legend(leg)
vpleg+<-+viewport(width+=+0.1,+height+=+0.1,+x=0.85,y=0.5)
layout(matrix(c(1,2),1,2,byrow=T),widths=c(3,1))
plot(t8g,edge.width=1,edge.arrow.size=0.1,vertex.label.cex=0.2,main="b2_top10")
pushViewport(vpleg)
grid.draw(legend)|code-block|syntax|javascript|279352|entityMap^0|0|V|8|14|8|0|A|D|S|7|10|3|0|C|3|0|7|3|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@$D|W|E|X|F|G]|$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|10|8|@$D|11|E|12|F|G]|$D|13|E|14|F|G]|$D|15|E|16|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|17|8|@$D|18|E|19|F|G]]|9|@]|A|$]]|$1|L|3|M|5|6|7|1A|8|@$D|1B|E|1C|F|G]]|9|@]|A|$]]|$1|N|3|O|5|P|7|1D|8|@]|9|@]|A|$Q|R]]|$1|S|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|T|$]]

<p>I was color coding the vertices in the graph and wanted to generate a legend as simply , elegantly and as quickly as I can.</p>

<p>The fastest way to do this I've come to believe is generate the legend separately using ggplot2 before "pasting" the legend into the same plot as igraph using <code>viewport</code> and <code>layout()</code></p>

<p>In this method there is no need to call the <code>rescale</code> or <code>asp</code> arguements in the <code>plot.igraph()</code> function.</p>

<p>Using the g_legend function on a data.frame, <code>leg</code>, with 2 columns, x being the appropriate vertex attribute and y being the hex colour code used in my igraph plot, I've done the following.</p>

<p>My igraph object is <code>t8g</code></p>

<pre><code>legend &lt;- g_legend(leg)
vpleg &lt;- viewport(width = 0.1, height = 0.1, x=0.85,y=0.5)
layout(matrix(c(1,2),1,2,byrow=T),widths=c(3,1))
plot(t8g,edge.width=1,edge.arrow.size=0.1,vertex.label.cex=0.2,main="b2_top10")
pushViewport(vpleg)
grid.draw(legend)
</code></pre>


blocks|key|496203|text|Cowplot很方便地添加了一个函数来提取图例。以下内容直接取自手册。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|496204|library(ggplot2)
library(cowplot)
p1+<-+ggplot(mtcars,+aes(mpg,+disp))+%2B+geom_line()
plot.mpg+<-+ggplot(mpg,+aes(x+=+cty,+y+=+hwy,+colour+=+factor(cyl)))+%2B+geom_point(size=2.5)

#+Note+that+these+cannot+be+aligned+vertically+due+to+the+legend+in+the+plot.mpg
ggdraw(plot_grid(p1,+plot.mpg,+ncol=1,+align='v'))

#+now+extract+the+legend
legend+<-+get_legend(plot.mpg)

#+and+replot+suppressing+the+legend
plot.mpg+<-+plot.mpg+%2B+theme(legend.position='none')

#+Now+plots+are+aligned+vertically+with+the+legend+to+the+right
ggdraw(plot_grid(plot_grid(p1,+plot.mpg,+ncol=1,+align='v'),
+++++++++++++++++plot_grid(NULL,+legend,+ncol=1),
+++++++++++++++++rel_widths=c(1,+0.2)))|code-block|syntax|javascript|496205|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>Cowplot handily adds a function to extract the legend. The following is taken directly from the manual. </p>

<pre><code>library(ggplot2)
library(cowplot)
p1 &lt;- ggplot(mtcars, aes(mpg, disp)) + geom_line()
plot.mpg &lt;- ggplot(mpg, aes(x = cty, y = hwy, colour = factor(cyl))) + geom_point(size=2.5)

# Note that these cannot be aligned vertically due to the legend in the plot.mpg
ggdraw(plot_grid(p1, plot.mpg, ncol=1, align='v'))

# now extract the legend
legend &lt;- get_legend(plot.mpg)

# and replot suppressing the legend
plot.mpg &lt;- plot.mpg + theme(legend.position='none')

# Now plots are aligned vertically with the legend to the right
ggdraw(plot_grid(plot_grid(p1, plot.mpg, ncol=1, align='v'),
                 plot_grid(NULL, legend, ncol=1),
                 rel_widths=c(1, 0.2)))
</code></pre>


blocks|key|496225|text|我使用了ggpubr包-让它变得非常简单！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|496226|https://rpkgs.datanovia.com/ggpubr/reference/get_legend.html|offset|length|496227|#+Extract+the+legend.+Returns+a+gtable
leg+<-+get_legend(p)

#+Convert+to+a+ggplot+and+print
as_ggplot(leg)|code-block|syntax|javascript|496228|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1O|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@$D|T|E|U|1|V]]|A|$]]|$1|F|3|G|5|H|7|W|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|C]]]]

<p>I used the ggpubr package - makes it very easy!</p>

<p><a href="https://rpkgs.datanovia.com/ggpubr/reference/get_legend.html" rel="noreferrer">https://rpkgs.datanovia.com/ggpubr/reference/get_legend.html</a></p>

<pre><code># Extract the legend. Returns a gtable
leg &lt;- get_legend(p)

# Convert to a ggplot and print
as_ggplot(leg)
</code></pre>


<p>I'm currently working with igraph and have colour labelled my vertices. I would like to add a legend Indicating what each colour represents. </p>

<p>What I can think of at this point is to use ggplot2 to print only the legend and hide a bar plot. 
Is there a way to just output the legend?</p>


How to plot just the legends in ggplot2?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我目前正在使用igraph，并用颜色标记了我的顶点。我想添加一个图例，指出每种颜色代表什么。此时，我能想到的是使用ggplot2仅打印图例并隐藏条形图。有什么方法可以直接输出图例吗？

问如何在ggplot2中只绘制图例？
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问如何在ggplot2中只绘制图例？EN