Here is an example with made-up sample data (BTW you should make your questions providing a REPRoducible EXample (reprex) as the one bellow).
library(tidyverse)
set.seed(123) # For reproducibility
sample_data <- data.frame(
weight = runif(10, 50, 80),
sex = sample(c("Male", "Female"), size = 20, replace = TRUE)
)
sample_data %>%
filter(sex == "Male") %>%
ggplot(aes(y = weight, x = sex)) +
geom_boxplot()
Created on 2020-02-02 by the reprex package (v0.3.0)