Plot multiple lines from multiple dataframes

Question

I have these piece of code to draw two line charts ( confirmed cases and death cases) How to show both curves in one chart with two dataframes (two ggplots)? Is it even possible or do I need to merge my two dataframes ( conf_data, dead_data ) into one data_frame ?

ggplot(conf_data, aes(x = date, y = confirmed)) +
        geom_line(colour = "blue", size =1.1, aes(date, confirmed)) +
        scale_y_continuous(labels = comma)

  ...

      ggplot(dead_data, aes(x = date, y = deaths)) +
        geom_line(colour = "red", size =1.1, aes(date, deaths)) +
        scale_y_continuous(labels = comma)

Here is my current working example with just one chart http://webcovid19.online/

It’s possible — but why not join the data? 9 out of 10 times that’s what you want to do. — Konrad Rudolph
– Konrad Rudolph, Commented Nov 25, 2020 at 14:16
yes, you have right, join is the best option ( also for performance, I hope) , but as you advised me also two dataframes option is working, let me check... :) — Andrew
– Andrew, Commented Nov 25, 2020 at 14:45

stevec · Accepted Answer · 2020-11-25 14:08:31Z

1

Does this work

library(tidyverse)

ggplot(conf_data, aes(x = date, y = confirmed)) +
        geom_line(colour = "blue", size =1.1, aes(date, confirmed)) +
        geom_line(colour = "red", size =1.1, aes(date, deaths)) +
        scale_y_continuous(labels = comma)

answered Nov 25, 2020 at 14:08

stevec

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Konrad Rudolph · Accepted Answer · 2020-11-25 14:17:43Z

0

You can pass custom data to a geometry via the data argument:

ggplot(conf_data, aes(x = date, y = confirmed)) +
    geom_line(color = "blue", size = 1.1, aes(date, confirmed)) +
    scale_y_continuous(labels = comma) +
    geom_line(color = "red", size = 1.1, aes(date, deaths), data = dead_data)

However, most of the time it’s more convenient to merge the data prior to plotting — if for no other reason, then because it allows you to create a proper legend and provide custom colour scales etc.:

bind_rows(
    transmute(conf_data, number = confirmed, type = 'confirmed'),
    transmute(death_data, number = deaths, type = 'deaths')
) %>%
    ggplot(aes(x = date, y = number, color = type, group = type)) +
    geom_line()

answered Nov 25, 2020 at 14:17

Konrad Rudolph

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2 Comments

Andrew Over a year ago

Hi Rudolph, I already use the 2nd option ( join dataframes ..), however is there some option to filter in multi charts ( countries in my case) to show only top 10 lines, to speed up ggplot ? Or I have to do it my self, filter dataframes before ggplot ? ( I did it already this way, see my site.)

Konrad Rudolph Over a year ago

@Andrew Unfortunately you have to do the filtering yourself, I’m not aware of an option inside ‘ggplot2’ to do the filtering.

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