Align 2 ggplot graphs on two different slides - r

Question

Dear All,
I want to make 2 choropleths to be put in 2 consecutive slides in a beamer presentation. The boundaries are the same but the fill color is different, so that when I go from the first slide to the second one,the map should not move, but only flip fill colors.
My problem is that I use the SAME incantation of ggplot (except for the fill colour) 2 times to make the 2 graphs and yet the 2 graphs are not aligned so that when I transition from the first slide to the second,I can see the second graph shift a little along the horizontal direction.
Due to the confidential nature of the data I am unable to paste my example.
# This example is from :
# https://medium.com/#anjesh/step-by-step-choropleth-map-in-r-a-case-of-mapping-nepal-7f62a84078d9
library(rgdal)
library(ggplot2)
library(dplyr)
library(broom)
# clone NepalMaps from https://github.com/anjesh/NepalMaps
# read shapefile
nepal.adm3.shp <- readOGR(dsn="./NepalMaps-master/baselayers/NPL_adm", layer="NPL_adm3", stringsAsFactors = FALSE)
# tidy shapefile data to data frame
nepal.adm3.shp.df <- tidy(nepal.adm3.shp, region = "NAME_3")
#write districts to csv file
mydata <- nepal.adm3.shp.df %>%
distinct(id) %>%
write.csv("districts.csv", row.names = FALSE)
mydata <- read.csv("districts.csv")
# Make fake data
mydata$Var1 = as.factor(sample(c(1:5,NA),nrow(mydata),replace= TRUE))
mydata$Var2 = as.factor(sample(c(1:5,NA),nrow(mydata),replace= TRUE))
mydata$Var3 = as.factor(sample(c(1:5,NA),nrow(mydata),replace= TRUE))
myshapeAndData <- left_join(nepal.adm3.shp.df,mydata,by="id")
library(scales)
library(ggplot2)
library(RColorBrewer)
# Plot using ggplot2.
# EXACT same Graphs,EXCEPT,with different lengths of title / legend title (padded with spaces to make them of equal length)
# The graphs move on transitioning from one slide to the other. I have padded the plot title / legend title with spaces to make them have the same length but it does NOT work.
ggplot() +
geom_polygon(data = myshapeAndData, aes(x=long,y=lat,group = group,fill = Var1),color= "black") +
scale_fill_manual(name ="Var1 ",values = brewer.pal(5,"Greens"),na.value = "pink") +
theme(plot.margin = unit(c(.4,.8,.3,.2), "in")) +
xlab("") +
ylab("") +
theme(legend.key.size = unit(1, "cm")) +
theme(legend.text=element_text(size=15),axis.text=element_text(size=15),plot.title = element_text(size=20),legend.title =element_text(size=15),axis.title = element_text(size=15)) +
ggtitle("Title Length 1 ") +
theme(plot.title = element_text(hjust = 0.5)) +
coord_fixed(ratio = 5.6/3.8)
ggsave("graph1.pdf",height =38/4,width = 56/4,units="in")
ggplot() +
geom_polygon(data = myshapeAndData, aes(x=long,y=lat,group = group,fill = Var2),color = "black") +
scale_fill_manual(name = "My var 2 ",values = brewer.pal(5,"Greens"),na.value = "pink") +
theme(plot.margin = unit(c(.4,.8,.3,.2), "in")) +
xlab("") +
ylab("") +
theme(legend.key.size = unit(1, "cm")) +
theme(legend.text=element_text(size=15),axis.text=element_text(size=15),plot.title = element_text(size=20),legend.title =element_text(size=15),axis.title = element_text(size=15)) +
ggtitle("My title Length 2 ") +
theme(plot.title = element_text(hjust = 0.5)) +
coord_fixed(ratio = 5.6/3.8)
ggsave("graph2.pdf",height = 38/4,width = 56/4,units="in")
ggplot() +
geom_polygon(data = myshapeAndData, aes(x=long,y=lat,group = group,fill = Var3),color = "black") +
scale_fill_manual(name = "3rd Variable",values = brewer.pal(5,"Greens") ,na.value = "pink") +
theme(plot.margin = unit(c(.4,.8,.3,.2), "in")) +
xlab("") +
ylab("") +
theme(legend.key.size = unit(1, "cm")) +
theme(legend.text=element_text(size=15),axis.text=element_text(size=15),plot.title = element_text(size=20),legend.title =element_text(size=15),axis.title = element_text(size=15)) +
ggtitle("My title-testing three") +
theme(plot.title = element_text(hjust = 0.5)) +
coord_fixed(ratio = 5.6/3.8)
ggsave("graph3.pdf",height = 38/4,width = 56/4,units="in")
# EXACT same graphs.
# All graphs with the same length of plot title and legend title.
# This works. The graphs do not move on transitioning,they only flip colors.
ggplot() +
geom_polygon(data = myshapeAndData, aes(x=long,y=lat,group = group,fill = Var1),color= "black") +
scale_fill_manual(name ="Var1",values = brewer.pal(5,"Greens"),na.value = "pink") +
theme(plot.margin = unit(c(.4,.8,.3,.2), "in")) +
xlab("") +
ylab("") +
theme(legend.key.size = unit(1, "cm")) +
theme(legend.text=element_text(size=15),axis.text=element_text(size=15),plot.title = element_text(size=20),legend.title =element_text(size=15),axis.title = element_text(size=15)) +
ggtitle("Title1") +
theme(plot.title = element_text(hjust = 0.5)) +
coord_fixed(ratio = 5.6/3.8)
ggsave("graph1.pdf",height =38/4,width = 56/4,units="in")
ggplot() +
geom_polygon(data = myshapeAndData, aes(x=long,y=lat,group = group,fill = Var2),color = "black") +
scale_fill_manual(name = "Var2",values = brewer.pal(5,"Greens"),na.value = "pink") +
theme(plot.margin = unit(c(.4,.8,.3,.2), "in")) +
xlab("") +
ylab("") +
theme(legend.key.size = unit(1, "cm")) +
theme(legend.text=element_text(size=15),axis.text=element_text(size=15),plot.title = element_text(size=20),legend.title =element_text(size=15),axis.title = element_text(size=15)) +
ggtitle("Title2") +
theme(plot.title = element_text(hjust = 0.5)) +
coord_fixed(ratio = 5.6/3.8)
ggsave("graph2.pdf",height = 38/4,width = 56/4,units="in")
ggplot() +
geom_polygon(data = myshapeAndData, aes(x=long,y=lat,group = group,fill = Var3),color = "black") +
scale_fill_manual(name = "Var3",values = brewer.pal(5,"Greens") ,na.value = "pink") +
theme(plot.margin = unit(c(.4,.8,.3,.2), "in")) +
xlab("") +
ylab("") +
theme(legend.key.size = unit(1, "cm")) +
theme(legend.text=element_text(size=15),axis.text=element_text(size=15),plot.title = element_text(size=20),legend.title =element_text(size=15),axis.title = element_text(size=15)) +
ggtitle("Title3") +
theme(plot.title = element_text(hjust = 0.5)) +
coord_fixed(ratio = 5.6/3.8)
ggsave("graph3.pdf",height = 38/4,width = 56/4,units="in")
Here is the latex file to display the graphs.
\documentclass{beamer}
\usetheme{CambridgeUS}
\usepackage{amssymb,amsmath}
\usepackage{listings}
\usepackage{hyperref}
\usepackage{fancyvrb}
\title[]{Testing maps}
\author{}
\begin{document}
\maketitle
\begin{frame}
\centering
\begin{tabular}{c}
\includegraphics[width=0.9\linewidth]{graph1.pdf}
\end{tabular}
\end{frame}
\begin{frame}
\centering
\begin{tabular}{c}
\includegraphics[width=0.9\linewidth]{graph2.pdf}
\end{tabular}
\end{frame}
\begin{frame}
\centering
\begin{tabular}{c}
\includegraphics[width=0.9\linewidth]{graph3.pdf}
\end{tabular}
\end{frame}
\end{document}