library(ggplot2)

count <- c(100,150,112)
cat <- c("A", "B", "C")
sentiment <- c(-0.3, 0.2, 0.8)
duration <- c(5.6, 8.2,5.2)
silence <- c(0.2, 0.05,0.1)

df <- data.frame(count, cat, sentiment, duration, silence)

p6 <- ggplot(df, aes(x = duration, y = silence, size = count, colour = sentiment)) + geom_point()
p7 <- p6 + scale_size_continuous(range = c(5, 8))
p7 + scale_x_continuous(limits = c(2, 10)) + scale_y_continuous(limits = c(0,0.25)) + theme(legend.position="none")