ggplot - How to set the bar itself to be colored by a color gradient (green->yellow->red)

Question

I want that the bars will be filled by the color gradient. Just to be clear, I don't mean to colored the whole bar with just one color based on the value and the gradient, like this:

scale_fill_gradient(low="green", high="red")

I mean gradient inside the bar itself, something like this:

What I'm trying to do is to create a kind of daily risk bar scale for 11 days and later on to add arrows to indicate the risk on each bar. It should look like this and I want that all the bars will be colored as the above bar pic.

    lines <- data.frame(day=c("Today", "Tomorrow","Day 3","Day 4","Day 5","Day 6","Day 7","Day 8","Day 9","Day 10","Day 11"),
                    a=rep(4,times=11))
lines$a <- as.numeric(lines$a)
order=c(1:11)

ggplot(lines, aes(x=reorder(day,-order),y=a, fill = a)) + 
       geom_bar(stat = "identity") +
       coord_flip()

By "bars" you mean one bar (ie, you want to plot on color gradient bar)? And how is this different from your [previous question](https://stackoverflow.com/questions/48645666/how-to-make-a-gradual-color-bar-for-representation-of-risk-analysis-results-in-r)? — pogibas, Feb 08 '18 at 13:45
Maybe [this](http://www.cookbook-r.com/Graphs/Colors_(ggplot2)/#continuous-colors) guide can help you obtain what you want. Note that variable which is set to color must be continuous. — Yatharth Malik, Feb 08 '18 at 13:47
@PoGibas - actually I need 11 bars in one figure that's why I'm trying to use ggplot and not plot (as my previous question). Yatharth Malik by using scale_*_gradient the bars are just in one color based on there values and the gradient.. — Bents, Feb 08 '18 at 13:56
Please provide some kind of data. Should color gradients be identical? — pogibas, Feb 08 '18 at 13:57
Please make a [reproducible example](http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) — emilliman5, Feb 08 '18 at 14:04
Yeah, please provide some data. If the bars only contain one color, it might be the case that you have specified the same column in `aes()` for `x =` and `fill =`. Make sure that `fill = `equals `y =` if you want the color gradient to apply to whatever is inside the bars — tifu, Feb 08 '18 at 14:06
@PoGibas is my question is clearer with the addition? yes the colors should move from green to red — Bents, Feb 08 '18 at 14:18

score 0 · Accepted Answer · answered Feb 08 '18 at 14:17

0

You need lots of bars.

lines <- expand.grid(day=c("Today", "Tomorrow","Day 3","Day 4","Day 5","Day 6","Day 7","Day 8","Day 9","Day 10","Day 11"),
                     x = 1:1000)
lines$day <- factor(lines$day, unique(lines$day))

ggplot(lines, aes(day, x, fill = x)) + 
    geom_bar(stat = "identity", show.legend = FALSE) +
    coord_flip() + 
    viridis::scale_fill_viridis()

You can change the fill scale, but I don't advise using red to green.

answered Feb 08 '18 at 14:17

Axeman

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Thanks for your answer! there is a way to change the colors to green-->red? – Bents Feb 08 '18 at 14:23
when Im running your code I get this error: arguments imply differing number of rows: 11, 1000 what should I change to make it works? – Bents Feb 08 '18 at 14:30
If I run the code exactly as written I get that figure. – Axeman Feb 08 '18 at 14:45
my mistake.. tanks a lot! – Bents Feb 08 '18 at 14:54

ggplot - How to set the bar itself to be colored by a color gradient (green->yellow->red)

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