[R] How to shade area between lines in ggplot2

PIKAL Petr petr@p|k@| @end|ng |rom prechez@@cz
Fri Oct 23 14:35:04 CEST 2020


Hi

What about something like

p+geom_ribbon(aes(ymin = slope_1*x + intercept_1 - 1/w[2],
ymax = slope_1*x + intercept_1 + 1/w[2], fill = "grey70", alpha=0.1))

Cheers
Petr

> -----Original Message-----
> From: Luigi Marongiu <marongiu.luigi using gmail.com>
> Sent: Friday, October 23, 2020 11:11 AM
> To: PIKAL Petr <petr.pikal using precheza.cz>
> Cc: r-help <r-help using r-project.org>
> Subject: Re: [R] How to shade area between lines in ggplot2
>
> also from this site: https://plotly.com/ggplot2/geom_ribbon/
> I get the answer is geom_ribbon but I am still missing something ``` #! plot 
> p
> = ggplot(data = trainset, aes(x=x, y=y, color=z)) +
>   geom_point() + scale_color_manual(values = c("red", "blue")) # show
> support vectors df_sv = trainset[svm_model$index, ] p = p +
> geom_point(data = df_sv, aes(x=x, y=y),
>                    color="purple", size=4, alpha=0.5) # show hyperplane 
> (decision
> boundaries are off set by 1/w[2]) w = t(svm_model$coefs) %*%
> svm_model$SV  # %*% = matrix multiplication
> slope_1 = -w[1]/w[2]
> intercept_1 = svm_model$rho / w[2]
> p = p + geom_abline(slope = slope_1, intercept = intercept_1, col =
> "royalblue4")
> p = p +     geom_ribbon(aes(ymin=intercept_1 - 1/w[2],
>                             ymax=intercept_1 + 1/w[2],
>                             x=x, fill = "band"), alpha = 0.3) +
>   scale_fill_manual("",values="grey12")
> ```
>
> On Fri, Oct 23, 2020 at 10:26 AM PIKAL Petr <petr.pikal using precheza.cz> wrote:
> >
> > Hi
> >
> > Did you try google? I got several answers using your question
> >
> > e.g.
> > https://stackoverflow.com/questions/54687321/fill-area-between-lines-u
> > sing-g
> > gplot-in-r
> >
> > Cheers
> > Petr
> >
> > > -----Original Message-----
> > > From: R-help <r-help-bounces using r-project.org> On Behalf Of Luigi
> > > Marongiu
> > > Sent: Friday, October 23, 2020 9:59 AM
> > > To: r-help <r-help using r-project.org>
> > > Subject: [R] How to shade area between lines in ggplot2
> > >
> > > Hello,
> > > I am running SVM and showing the results with ggplot2. The results
> > > include the decision boundaries, which are two dashed lines parallel
> > > to a solid
> > line. I
> > > would like to remove the dashed lines and use a shaded area instead.
> > > How can I do that?
> > > Here is the code I wrote..
> > > ```
> > > library(e1071)
> > > library(ggplot2)
> > >
> > > set.seed(100)
> > > x1 = rnorm(100, mean = 0.2, sd = 0.1)
> > > y1 = rnorm(100, mean = 0.7, sd = 0.1)
> > > y2 = rnorm(100, mean = 0.2, sd = 0.1)
> > > x2 = rnorm(100, mean = 0.75, sd = 0.1) df = data.frame(x = c(x1,x2),
> > > y=c(y1,y2),
> > >                 z=c(rep(0, length(x1)), rep(1, length(x2)))) df$z =
> > factor(c(rep(0,
> > > length(x1)), rep(1, length(x2)))) df[, "train"] <-
> > > ifelse(runif(nrow(df))
> > < 0.8, 1, 0)
> > > trainset <- df[df$train == 1, ] testset <- df[df$train == 0, ]
> > > trainColNum
> > <-
> > > grep("train", names(df)) trainset <- trainset[, -trainColNum]
> > > testset <-
> > testset[,
> > > -trainColNum] head(trainset); str(df)
> > >
> > > svm_model<- svm(z ~ .,
> > >                 data = trainset,
> > >                 type = "C-classification",
> > >                 kernel = "linear",
> > >                 scale = FALSE)
> > >
> > > #! plot
> > > p = ggplot(data = trainset, aes(x=x, y=y, color=z)) +
> > >   geom_point() + scale_color_manual(values = c("red", "blue")) #
> > > show decision boundaries w = t(svm_model$coefs) %*% svm_model$SV
> #
> > > %*% = matrix multiplication
> > > slope_1 = -w[1]/w[2]
> > > intercept_1 = svm_model$rho / w[2]
> > > p = p + geom_abline(slope = slope_1, intercept = intercept_1) ###
> > > here we
> > go:
> > > can I use a shaded area between these two lines? ### p = p +
> > > geom_abline(slope = slope_1, intercept = intercept_1 - 1/w[2],
> > >                     linetype = "dashed") +
> > >   geom_abline(slope = slope_1, intercept = intercept_1 + 1/w[2],
> > >               linetype = "dashed")
> > > print(p)
> > >
> > > ```
> > >
> > > Thank you
> > >
> > > --
> > > Best regards,
> > > Luigi
> > >
> > > ______________________________________________
> > > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > PLEASE do read the posting guide http://www.R-project.org/posting-
> > > guide.html and provide commented, minimal, self-contained,
> > > reproducible code.
>
>
>
> --
> Best regards,
> Luigi


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