title: Change distance between x-axis ticks in ggplot2
body: <p>Right now I am producing a line graph with three observations. Hence, there are three x-axis ticks. </p>
  
  <p>I want to manually reduce the distance between the x-axis ticks and basically force the observations to be closer to each other. In other words, I want to reduce the distance between the x-axis ticks.</p>
  
  <p>My data:</p>
  
  <pre><code>structure(list(Period = c("January 1997 - August 2003", "September 2003 - Jun 2005", 
  "Jul 2005 - Dec 2009", "January 1997 - August 2003", "September 2003 - Jun 2005", 
  "Jul 2005 - Dec 2009"), Time.Period = structure(c(1L, 3L, 2L, 
  1L, 3L, 2L), .Label = c("Jan 1997 - Aug 2003", "Jul 2005 - Dec 2009", 
  "Sep 2003 - Jun 2005"), class = "factor"), Variable = structure(c(2L, 
  2L, 2L, 1L, 1L, 1L), .Label = c("Significant", "Zscore"), class = "factor"), 
  Score = c(8.798129, 4.267268, 7.280275, 1.64, 1.64, 1.64)), .Names = c("Period", 
  "Time.Period", "Variable", "Score"), class = "data.frame", row.names = c(NA, 
  -6L))
  </code></pre>
  
  <p>My code:</p>
  
  <pre><code>ggplot(glomor, aes(x=Time.Period, y=Score, group=Variable, shape=Variable, color=Variable,        width=0.5)) +
  geom_point() +
  scale_x_discrete(limits=c("Jan 1997 - Aug 2003","Sep 2003 - Jun 2005","Jul 2005 - Dec 2009"),   expand=c(.08,0)) +
  geom_line(aes(linetype=Variable), size=1.3) +
  geom_point(size=4.4) +
  scale_shape_discrete(name="", label=c("Signficant Z-Score", "Moran's I Z-Score")) +
  scale_linetype_manual(values=c(1,3), name="", label=c("Signficant Z-Score", "Moran's I Z-Score"))   +
  scale_color_manual(values=c("black", "grey40"), name="", label=c("Signficant Z-Score", "Moran's I Z-Score")) +
  scale_fill_discrete(name="", label=c("Signficant Z-Score", "Moran's I Z-Score")) +
  theme_classic()+
  ylim(0,10) +
  xlab("Time Periods") +
  ylab("Moran's I Z-Score") +
  theme(axis.text.x=element_text(size=11)) +
  theme(axis.title.x=element_text(size=14, face="bold")) +
  theme(axis.title.y=element_text(size=14, face="bold")) +
  theme(legend.position=c(.80, .90)) +
  theme(legend.text=element_text(size=12)) +
  theme(legend.background = element_rect(fill="white", linetype="dashed")) +
  theme(legend.key = element_blank()) 
  </code></pre>