Density plots of four groups in the same plot

Question

I am trying to plot density plots of four different groups in the same graph, but I somehow only get a plot of all data. How do I get four different plots in the same graph grouped by my parameter df$gr?

My script:

ggplot(df, aes(x = LENGTH,y=..count..,fill=gr)) +
  geom_density(alpha=0.6) +
  scale_color_manual(values = c("red", "green","blue","yellow")) +
  theme_bw()

and a data frame:

dput(df)
structure(list(LENGTH = c(21, 20, 17, 23, 22, 22, 16, 23, 16, 
18, 15, 19, 18, 18, 16, 16, 16, 16, 18, 22, 19, 18, 18, 18, 16, 
19, 16, 18, 19, 17, 22, 20, 22, 18, 17, 20, 18, 18, 17, 18, 19, 
17, 17, 19, 18, 18, 17, 20, 18, 19, 17, 18, 17, 17, 17, 19, 19, 
17, 18, 18, 17, 20, 18, 18, 19, 17, 17, 17, 18, 18, 25, 24, 24, 
23, 17, 15, 23, 23, 21, 22, 18, 18, 16, 19, 16, 16, 15, 15, 17, 
15, 16, 15, 17, 18, 20, 18, 14, 19, 18, 19, 19, 20, 22, 18, 20, 
21, 17, 17, NA, NA, NA, NA, 20, 18, 17, 23, 19, 20, 18, 19, 17, 
17, 16, 18, 17, 17, 19, 18, 20, 23, 19, 19, 20, 19, 14, 18, 20, 
20, 18, 20, 19, 14, 18, 19, 17, 18, 9, 22, 22, 18, 17, 17, 19, 
16, 17, 16, 17, 17, 18, 17, 16), gr = c(1, 1, 2, 1, 1, 2, 1, 
1, 2, 1, 2, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 
1, 2, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 
1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 
1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 4, 4, 4, 3, 4, 3, 4, 4, 3, 4, 3, 
3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 3, 3, 3, 4, 4, 4, 3, 3, 3, 3, 
3, 3, 3, 3, 3, 3, 4, 3, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 
4, 3, 3, 3, 3, 3, 4, 3, 4, 3, 4, 4, 4, 3, 3, 4, 3, 4, 4, 3, 4, 
3, 4, 4, 4, 3, 3, 4)), row.names = c(1508L, 1509L, 1510L, 1511L, 
1512L, 1513L, 1514L, 1515L, 1516L, 1517L, 1518L, 1519L, 1520L, 
1521L, 1522L, 1523L, 1524L, 1525L, 1526L, 1527L, 1528L, 1529L, 
1530L, 1531L, 1532L, 1533L, 1534L, 1535L, 1536L, 1537L, 1538L, 
1539L, 1540L, 1541L, 1542L, 1543L, 1544L, 1545L, 1546L, 1547L, 
1548L, 1549L, 1550L, 1551L, 1552L, 1553L, 1554L, 1555L, 1556L, 
1557L, 1558L, 1559L, 1560L, 1561L, 1562L, 1563L, 1564L, 1565L, 
1566L, 1567L, 1568L, 1569L, 1570L, 1571L, 1572L, 1573L, 1574L, 
1575L, 1576L, 1577L, 1578L, 1579L, 1580L, 1581L, 1582L, 1583L, 
1584L, 1585L, 1586L, 1587L, 2277L, 2278L, 2279L, 2280L, 2281L, 
2282L, 2283L, 2284L, 2285L, 2286L, 2287L, 2288L, 2289L, 2290L, 
2291L, 2292L, 2293L, 2294L, 2295L, 2296L, 2297L, 2298L, 2299L, 
2300L, 2301L, 2302L, 2303L, 2304L, 2305L, 2306L, 2307L, 2308L, 
2309L, 2310L, 2311L, 2312L, 2313L, 2314L, 2315L, 2316L, 2317L, 
2318L, 2319L, 2320L, 2321L, 2322L, 2323L, 2324L, 2325L, 2326L, 
2327L, 2328L, 2329L, 2330L, 2331L, 2332L, 2333L, 2334L, 2335L, 
2336L, 2337L, 2338L, 2339L, 2340L, 2341L, 2342L, 2343L, 2344L, 
2345L, 2346L, 2347L, 2348L, 2349L, 2350L, 2351L, 2352L, 2353L, 
2354L, 2355L, 2356L, 2357L), class = "data.frame")

score 2 · Accepted Answer · answered May 10 '20 at 16:53

Your gr field is numeric. Converting it to factor within the aes() argument was the solution:

ggplot(df, aes(x = LENGTH,y=..count..,fill=factor(gr))) +
  geom_density(alpha=0.6) +
  scale_color_manual(values = c("red", "green","blue","yellow")) +
  theme_bw()

score 1 · Answer 2 · answered May 10 '20 at 16:55

You have two issues. First, you need to make df$gr a factor. Second, you want to be careful of the difference between color and fill. Fill what is under the density curve and color is the line of the density curve. I imagine you want one of these:

df$gr = factor(df$gr)    
ggplot(df, aes(x = LENGTH,y=..count..,fill=gr)) +
      geom_density(alpha=0.6) +
      scale_fill_manual(values = c("red", "green","blue","yellow")) +
      theme_bw()

or

df$gr = factor(df$gr)
ggplot(df, aes(x = LENGTH,y=..count..,color=gr)) +
  geom_density(alpha=0.6) +
  scale_color_manual(values = c("red", "green","blue","yellow")) +
  theme_bw()

score 1 · Answer 3 · edited May 10 '20 at 21:26

You mean this?

dd = structure(
  list(
    LENGTH = c(21, 20, 17, 23, 22, 22, 16, 23, 16, 
               18, 15, 19, 18, 18, 16, 16, 16, 16, 18, 22, 19, 18, 18, 18, 16, 
               19, 16, 18, 19, 17, 22, 20, 22, 18, 17, 20, 18, 18, 17, 18, 19, 
               17, 17, 19, 18, 18, 17, 20, 18, 19, 17, 18, 17, 17, 17, 19, 19, 
               17, 18, 18, 17, 20, 18, 18, 19, 17, 17, 17, 18, 18, 25, 24, 24, 
               23, 17, 15, 23, 23, 21, 22, 18, 18, 16, 19, 16, 16, 15, 15, 17, 
               15, 16, 15, 17, 18, 20, 18, 14, 19, 18, 19, 19, 20, 22, 18, 20, 
               21, 17, 17, NA, NA, NA, NA, 20, 18, 17, 23, 19, 20, 18, 19, 17, 
               17, 16, 18, 17, 17, 19, 18, 20, 23, 19, 19, 20, 19, 14, 18, 20, 
               20, 18, 20, 19, 14, 18, 19, 17, 18, 9, 22, 22, 18, 17, 17, 19, 
               16, 17, 16, 17, 17, 18, 17, 16), 
    gr = c(1, 1, 2, 1, 1, 2, 1, 
           1, 2, 1, 2, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 
           1, 2, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 
           1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 
           1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 4, 4, 4, 3, 4, 3, 4, 4, 3, 4, 3, 
           3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 3, 3, 3, 4, 4, 4, 3, 3, 3, 3, 
           3, 3, 3, 3, 3, 3, 4, 3, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 
           4, 3, 3, 3, 3, 3, 4, 3, 4, 3, 4, 4, 4, 3, 3, 4, 3, 4, 4, 3, 4, 
           3, 4, 4, 4, 3, 3, 4)), 
  row.names = c(1508L, 1509L, 1510L, 1511L, 
                1512L, 1513L, 1514L, 1515L, 1516L, 1517L, 1518L, 1519L, 1520L, 
                1521L, 1522L, 1523L, 1524L, 1525L, 1526L, 1527L, 1528L, 1529L, 
                1530L, 1531L, 1532L, 1533L, 1534L, 1535L, 1536L, 1537L, 1538L, 
                1539L, 1540L, 1541L, 1542L, 1543L, 1544L, 1545L, 1546L, 1547L, 
                1548L, 1549L, 1550L, 1551L, 1552L, 1553L, 1554L, 1555L, 1556L, 
                1557L, 1558L, 1559L, 1560L, 1561L, 1562L, 1563L, 1564L, 1565L, 
                1566L, 1567L, 1568L, 1569L, 1570L, 1571L, 1572L, 1573L, 1574L, 
                1575L, 1576L, 1577L, 1578L, 1579L, 1580L, 1581L, 1582L, 1583L, 
                1584L, 1585L, 1586L, 1587L, 2277L, 2278L, 2279L, 2280L, 2281L, 
                2282L, 2283L, 2284L, 2285L, 2286L, 2287L, 2288L, 2289L, 2290L, 
                2291L, 2292L, 2293L, 2294L, 2295L, 2296L, 2297L, 2298L, 2299L, 
                2300L, 2301L, 2302L, 2303L, 2304L, 2305L, 2306L, 2307L, 2308L, 
                2309L, 2310L, 2311L, 2312L, 2313L, 2314L, 2315L, 2316L, 2317L, 
                2318L, 2319L, 2320L, 2321L, 2322L, 2323L, 2324L, 2325L, 2326L, 
                2327L, 2328L, 2329L, 2330L, 2331L, 2332L, 2333L, 2334L, 2335L, 
                2336L, 2337L, 2338L, 2339L, 2340L, 2341L, 2342L, 2343L, 2344L, 
                2345L, 2346L, 2347L, 2348L, 2349L, 2350L, 2351L, 2352L, 2353L, 
                2354L, 2355L, 2356L, 2357L), 
  class = "data.frame"
)

library(ggplot2)
dd$gr = factor(dd$gr)
ggplot(dd, aes(x = LENGTH, y = ..count.., fill = gr)) +
  geom_density(alpha = 0.6) +
  scale_color_manual(values = c("red", "green", "blue", "yellow")) +
  theme_bw()

Density plots of four groups in the same plot

3 Answers3

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