diff --git a/config.toml b/config.toml
index b6c7f36..e00c09c 100644
--- a/config.toml
+++ b/config.toml
@@ -134,3 +134,8 @@ expiryDate = ["expiryDate"]
     name = "Impressum"
     url = "impressum/"
     weight = 30
+
+  [[menu.main]]
+    name = "Cheat sheet"
+    url = "cheatsheet/"
+    weight = 15
diff --git a/content/cheatsheet.md b/content/cheatsheet.md
new file mode 100644
index 0000000..37d5803
--- /dev/null
+++ b/content/cheatsheet.md
@@ -0,0 +1,97 @@
+---
+title: bovender's personal cheat sheet
+description: >
+  On this page, I collect bits and pieces of information that I
+  never seem to be able to memorize. This stuff is helpful for me
+  and maybe it is helpful for you, too, internet wanderer.
+date: 2024-11-05T08:00:00+0100
+draft: false
+---
+{{< git-info >}}
+{{< param "description" >}}
+
+## R
+
+### Print R objects so that they can be re-generated from code
+
+```r
+# dput takes an R object
+dput(x, file = "", control = c("keepNA", "keepInteger", "niceNames", "showAttributes"))
+dget(file, keep.source = FALSE)
+
+# dump takes a list of R object names
+dump(list, file = "dumpdata.R", append = FALSE, control = "all", envir = parent.frame(), evaluate = TRUE)
+```
+
+Example:
+
+``` r
+library(dplyr)
+my_data <-
+  starwars |>
+  select(species, homeworld)
+dput(my_data)
+#> structure(list(species = c("Human", "Droid", "Droid", "Human", 
+#> "Human", "Human", "Human", "Droid", "Human", "Human", "Human", 
+#> "Human", "Wookiee", "Human", "Rodian", "Hutt", "Human", NA, "Yoda's species", 
+#> "Human", "Human", "Droid", "Trandoshan", "Human", "Human", "Mon Calamari", 
+#> "Human", "Human", "Ewok", "Sullustan", "Human", "Neimodian", 
+#> "Human", "Human", "Gungan", "Gungan", "Gungan", "Human", "Toydarian", 
+#> "Dug", "Human", "Human", "Zabrak", "Twi'lek", "Twi'lek", "Aleena", 
+#> "Vulptereen", "Xexto", "Toong", "Human", "Cerean", "Nautolan", 
+#> "Zabrak", "Tholothian", "Iktotchi", "Quermian", "Kel Dor", "Chagrian", 
+#> NA, NA, "Human", "Geonosian", "Mirialan", "Mirialan", "Human", 
+#> "Human", "Human", "Human", "Clawdite", "Besalisk", "Kaminoan", 
+#> "Kaminoan", "Human", "Droid", "Skakoan", "Muun", "Togruta", "Kaleesh", 
+#> "Wookiee", "Human", NA, "Pau'an", "Human", "Human", "Human", 
+#> "Droid", "Human"), homeworld = c("Tatooine", "Tatooine", "Naboo", 
+#> "Tatooine", "Alderaan", "Tatooine", "Tatooine", "Tatooine", "Tatooine", 
+#> "Stewjon", "Tatooine", "Eriadu", "Kashyyyk", "Corellia", "Rodia", 
+#> "Nal Hutta", "Corellia", "Bestine IV", NA, "Naboo", "Kamino", 
+#> NA, "Trandosha", "Socorro", "Bespin", "Mon Cala", "Chandrila", 
+#> NA, "Endor", "Sullust", NA, "Cato Neimoidia", "Coruscant", "Naboo", 
+#> "Naboo", "Naboo", "Naboo", "Naboo", "Toydaria", "Malastare", 
+#> "Naboo", "Tatooine", "Dathomir", "Ryloth", "Ryloth", "Aleen Minor", 
+#> "Vulpter", "Troiken", "Tund", "Haruun Kal", "Cerea", "Glee Anselm", 
+#> "Iridonia", "Coruscant", "Iktotch", "Quermia", "Dorin", "Champala", 
+#> "Naboo", "Naboo", "Tatooine", "Geonosis", "Mirial", "Mirial", 
+#> "Naboo", "Serenno", "Alderaan", "Concord Dawn", "Zolan", "Ojom", 
+#> "Kamino", "Kamino", "Coruscant", NA, "Skako", "Muunilinst", "Shili", 
+#> "Kalee", "Kashyyyk", "Alderaan", "Umbara", "Utapau", NA, NA, 
+#> NA, NA, NA)), row.names = c(NA, -87L), class = c("tbl_df", "tbl", 
+#> "data.frame"))
+```
+
+<sup>Created on 2024-11-05 with [reprex v2.1.1](https://reprex.tidyverse.org)</sup>
+
+### Calculate percentages of subgroups
+
+Principle: `Group` the dataset and `summarize` by counting (`n()`), drop the last group
+while doing so, then `mutate` the dataset by adding the count divided by the sum of counts.
+
+Hint to better understand the example: Look at the sexes in black-eyed subjects.
+
+``` r
+library(dplyr)
+starwars |>
+  group_by(eye_color, gender) |>
+  summarize(n = n(), .groups = "drop_last") |>
+  mutate(p = n/sum(n))
+#> # A tibble: 23 × 4
+#> # Groups:   eye_color [15]
+#>    eye_color gender        n      p
+#>    <chr>     <chr>     <int>  <dbl>
+#>  1 black     feminine      2 0.2   
+#>  2 black     masculine     8 0.8   
+#>  3 blue      feminine      6 0.316 
+#>  4 blue      masculine    12 0.632 
+#>  5 blue      <NA>          1 0.0526
+#>  6 blue-gray masculine     1 1     
+#>  7 brown     feminine      4 0.190 
+#>  8 brown     masculine    15 0.714 
+#>  9 brown     <NA>          2 0.0952
+#> 10 dark      masculine     1 1     
+#> # ℹ 13 more rows
+```
+
+<sup>Created on 2024-11-05 with [reprex v2.1.1](https://reprex.tidyverse.org)</sup>