在RMarkdown中抑制marmap消息

假设我有以下RMarkdown文件:

---
title: "Test"
author: "Mr. Test"
date: "October 15, 2018"
output: html_document
---

```{r echo = FALSE, message = FALSE, error = FALSE, warning = FALSE}
# Load library
library(marmap)

# Download bathymetry data and keep for future use
bathy <- getNOAA.bathy(lon1 = -5, lon2 = 5, lat1 = -5, lat2 = 5, resolution = 1, keep = TRUE)

# Perform same command again, which reads downloaded file
invisible(bathy <- getNOAA.bathy(lon1 = -5, lon2 = 5, lat1 = -5, lat2 = 5, resolution = 1, keep = TRUE))
```

marmap 包下载一些数据并加载到R。然后,它再次从本地文件加载数据。这将产生以下输出:

invisible 但我还是得到了输出。查看原始代码 getNOAA.bathy ,我看到作者正在使用 cat 打印输出而不是 message . 在这种情况下,如何使函数静音?