How to format number of digits with kable

I want to format x and y using 3 digits: e.g. for x I want to obtain 0.035, 0.790, 0.453.

I tried using the following, without success:

---title: "format 3 digits"output:  word_document: default---```{r echo=FALSE,message=FALSE, warning=FALSE}library(tidyverse)library(knitr)df <- tibble(x = c(0.0345, 0.7898, 0.4534),             y = c(-0.0345, -0.7898, -0.4534),             z = c(1, 2, 3))df %>%  mutate_if(is.numeric, format, digits=3, nsmall=0) %>%  kable(.)```