[R] How to shade area between lines in ggplot2

[Luigi Marongiu]

Thank you, but this split the area into two and distorts the shape of
the plot. (compared to
```
p + geom_abline(slope = slope_1, intercept = intercept_1 - 1/w[2],
                    linetype = "dashed", col = "royalblue") +
  geom_abline(slope = slope_1, intercept = intercept_1 + 1/w[2],
              linetype = "dashed", col = "royalblue")
```

Why there is a hole in the middle of the ribbon? and the color is not grey...

On Fri, Oct 23, 2020 at 2:35 PM PIKAL Petr <petr.pikal using precheza.cz> wrote:
>
> 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



-- 
Best regards,
Luigi