Drawing very long legend at the bottom of scatterplot3d

Question

How I can put a very long legend at the bottom of the scatterplot3d plot properly? I tried to use layout, oma, mar, but I couldn't figure it out. What I want to have is having the plot at the top and putting the legend at the bottom. I can not proceed further. I really need help :(

Here is the code I tried so far:

library("scatterplot3d")


mean_E = c(2.5459233083,-1.75924812,-1.48706767,-1.70857143,-1.7201293233,2.1565954887,-1.3398496,3.353383,-0.96511278,2.81007519,0.8252120301,0.7203008,-1.2539834586,-1.5503759,0.67669,-0.0421053)
mean_P = c(1.02256,-1.744361,-1.56391,0.390977,-0.9819549,1.76015038,-1.962406,2.6294015038,0.526316,2.9744361,0.9172932,0.6315789,-0.6210526,0.93985,1.4208105263,0.406015)
mean_A = c(0.09023,-0.5714,-0.6165414,-0.428571,0.225564,0.80766917,-0.64180451,1.6967218045,-0.030075,2.6631579,0.5714286,0.1609023,-0.7487218,0.3619112782,1.7578947,0.3729323)
statementNameList = c("Sentence Sentence Sentence Sentence Sentence Sentence 1",
"Sentence Sentence Sentence Sentence Sentence Sentence 2",
"Sentence Sentence Sentence Sentence Sentence Sentence 3",
"Sentence Sentence Sentence Sentence Sentence Sentence 4",
"Sentence Sentence Sentence Sentence Sentence Sentence 5",
"Sentence Sentence Sentence Sentence Sentence Sentence 6",
"Sentence Sentence Sentence Sentence Sentence Sentence 7",
"Sentence Sentence Sentence Sentence Sentence Sentence 8",
"Sentence Sentence Sentence Sentence Sentence Sentence 9",
"Sentence Sentence Sentence Sentence Sentence Sentence 10",
"Sentence Sentence Sentence Sentence Sentence Sentence 11",
"Sentence Sentence Sentence Sentence Sentence Sentence 12",
"Sentence Sentence Sentence Sentence Sentence Sentence 13",
"Sentence Sentence Sentence Sentence Sentence Sentence 14",
"Sentence Sentence Sentence Sentence Sentence Sentence 15",
"Sentence Sentence Sentence Sentence Sentence Sentence 16")

mean_df <- data.frame("E"=mean_E,"P"=mean_P,"A"=mean_A,"Sentence"=statementNameList)

expressions <- data.frame("E"=c(-1.569,1.4796,-2.3793,3.4469,-2.4077, 2.8125,-2.5706,  3.0389,-2.09,-2.2676, -2.0267),
                          "P"=c(-1.1345,1.3151,-1.3414,2.9125,-0.7577, 2.2475,0.2676, 1.8417,-0.7833, -0.3514, 1.0667 ),
                          "A"=c(-2.0621,2.3139,-1.8759,0.2438,-0.6808, 2.16,0.4265, -2.7889,-2.19,0.7243,1.7967),
                          "Emotion"= c("Tired", "Surprised", "Sad", "Happy", "Fearful", "Excited", "Disgusted", "Calm", "Bored", "Annoyed", "Angry") )


title="EPA Ratings"
xlabel = "Evaluation (E)"
ylabel = "Potency (P)"
zlabel = "Activitiy (A)"
angle = -70


plot<-scatterplot3d(expressions$E ,expressions$P,expressions$A, main=title,
                    xlab=xlabel, ylab=ylabel, zlab=zlabel, pch = "", grid=TRUE, box=TRUE,
                    angle = angle)
plot$points3d(expressions$E ,expressions$P,expressions$A, pch = 5, col="red")

color_palette = grDevices::colors()[grep('gr(a|e)y', grDevices::colors(), invert = T)]
# select different color for each sentence
colors =sample(color_palette, 16)
plot$points3d(mean_df$E ,mean_df$P,mean_df$A, pch = 16, col=colors, cex=2)

legend(3,-3, legend = statementNameList,col = colors, pch = 16, inset = -0.5, cex = 0.7,
        bty = "n",xpd = TRUE)

text(plot$xyz.convert(expressions$E ,expressions$P,expressions$A-0.2), labels = expressions$Emotion, col = "darkblue", cex=0.6)

Here is the current output I have:

Answer 1

May be you can try below code. I found that in this link. http://www.sthda.com/english/wiki/scatterplot3d-3d-graphics-r-software-and-data-visualization

Custom shapes/colors

s3d <- scatterplot3d(iris[,1:3], pch = shapes, color=colors)
legend("bottom", legend = levels(iris$Species),
      col =  c("#999999", "#E69F00", "#56B4E9"), 
      pch = c(16, 17, 18), 
      inset = -0.25, xpd = TRUE, horiz = TRUE)