The y-axis: to zero or not to zero

This article tells us that “it’s OK not to start your y-axis at zero”, but then states that “column and bar charts should always have zeroed axes”. They use a chart from the Twitter IPO as an example. If you were waiting for the obligatory bad-mouthing of Excel, look no further than a follow-up Tweet by the chart author. @DocJohnG True. Also contact Microsoft Excel, let them know the default y-axis is simply unacceptable; lazy people like me need nudging. — D Yanagizawa-Drott (@yanagiz) November 11, 2016 Onwards. What if we use a line chart instead? ggplot(subset(elections.2, vote == "pop" & year > 2004), aes(year, value)) + geom_line(aes(color = variable)) + geom_point() + scale_x_continuous(breaks = seq(1980, 2016, 4)) + scale_color_manual(values = c("blue", "red")) + scale_y_continuous(labels = comma) + theme_bw() + labs(title = "US Election Popular vote 2008 - 2016") ggplot2 line chart with default y-axis scaleNow ggplot2 thinks that it’s fine to use a non-zero y-axis. The eye no longer compares absolute heights. How does the line chart look if we force the y-axis back to starting at zero? ggplot(subset(elections.2, vote == "pop" & year > 2004), aes(year, value)) + geom_line(aes(color = variable)) + geom_point() + scale_x_continuous(breaks = seq(1980, 2016, 4)) + scale_color_manual(values = c("blue", "red")) + scale_y_con...
Source: What You're Doing Is Rather Desperate - Category: Bioinformatics Authors: Tags: R statistics charts graph politics visualisation Source Type: blogs