Winter25 data summarization

modules/Data_Summarization/Data_Summarization.Rmd

@@ -8,11 +8,8 @@ output:
 
 
 ```{r, echo = FALSE, message=FALSE, error = FALSE}
-library(knitr)
-opts_chunk$set(comment = "", message = FALSE)
-suppressWarnings({library(dplyr)})
-library(readr)
-library(tidyverse)
+knitr::opts_chunk$set(comment = "", message = FALSE)
+suppressWarnings(library(tidyverse))
 ```
 
 <style type="text/css">
@@ -38,7 +35,7 @@ pre { /* Code block - slightly smaller in this lecture */
 
 https://raw.githubusercontent.com/rstudio/cheatsheets/main/data-transformation.pdf
 
-```{r, fig.alt="A preview of the Data transformation cheatsheet produced by RStudio.", out.width = "80%", echo = FALSE, align = "center"}
+```{r, fig.alt="A preview of the Data transformation cheatsheet produced by RStudio.", out.width = "80%", echo = FALSE, fig.align = "center"}
 knitr::include_graphics("images/Manip_cheatsheet.png")
 ```
 
@@ -99,7 +96,9 @@ sum(z)
 
 ## Some examples
 
-We can use the `mtcars` built-in dataset.  The `head` command displays the first rows of an object:
+We can use the `mtcars` built-in dataset. "The data was extracted from the 1974 Motor Trend US magazine, and comprises fuel consumption and 10 aspects of automobile design and performance for 32 automobiles (1973-74 models)."
+
+The `head` command displays the first rows of an object:
 
 ```{r}
 head(mtcars)
@@ -112,23 +111,10 @@ A nice and readable way to chain together multiple R functions.
 
 Changes `f(x, y)` to `x %>% f(y)`.
 
-```{r eval=FALSE}
-# Going to work
-get_dressed(me,
-            pack_lunch(
-              check_pockets(
-                wallet = TRUE, phone = TRUE, keys = TRUE),
-              items = c("sandwich", "chips", "apple"), lunchbox = TRUE),
-            pants = TRUE, shirt = TRUE, footwear = "sandals")
-
-# Going to work, the tidy way
-me %>%
-  get_dressed(pants = TRUE, shirt = TRUE, footwear = "sandals") %>%
-  pack_lunch(items = c("sandwich", "chips", "apple"), lunchbox = TRUE) %>%
-  check_pockets(wallet = TRUE, phone = TRUE, keys = TRUE)
+```{r, out.width = "50%", echo = FALSE, fig.align = "center"}
+knitr::include_graphics("../../images/lol/morning_1.png")
 ```
 
-
 ## Statistical summarization the "tidy" way
 
 ```{r}
@@ -141,7 +127,7 @@ mtcars %>% pull(wt) %>% quantile(probs = 0.6)
 
 ## Behavior of `pull()` function
 
-`pull()` converts a single data column into a vector. This allows you to run summary functions on these data. Once you have "pulled" the data column out, you don't have to name it again in any piped summary functions.
+`pull()` converts a single data column into a <span style="color:blue">vector</span>. This allows you to run summary functions on these data. Once you have "pulled" the data column out, you don't have to name it again in any piped summary functions.
 
 ```{r}
 cars_wt <- mtcars %>% pull(wt)
@@ -157,18 +143,29 @@ mtcars %>% pull(wt) %>% range(wt) # Incorrect
 mtcars %>% pull(wt) %>% range() # Correct
 ```
 
+## GUT CHECK
+
+What kind of object do we need to run summary operators like `mean()` ?
+
+A. A vector of numbers
+
+B. A vector of characters
+
+C. A dataset
 
 # Summarization on tibbles (data frames)
 
-## TB Incidence 
+## TB incidence
 
 Let's read in a `tibble` of values from TB incidence.
 
+"Tuberculosis incidence, all forms (per 100,000 population per year), for the period 1990-2007 across 208 countries/territories."
+
 ```{r}
 tb <- read_csv("https://jhudatascience.org/intro_to_r/data/tb.csv")
 ```
 
-## TB Incidence 
+## TB incidence 
 
 Check out the data:
 
@@ -177,7 +174,7 @@ head(tb)
 ```
 
 
-## TB Incidence 
+## TB incidence 
 
 Check out the data:
 
@@ -193,7 +190,6 @@ Before we go further, let's rename the first column using the `rename()` functio
 In this case, we have to use the backticks (\`) because there are spaces and funky characters in the name. 
 
 ```{r}
-library(dplyr)
 tb <- tb %>%
   rename(country = `TB incidence, all forms (per 100 000 population per year)`)
 ```
@@ -220,8 +216,8 @@ You can also do more elaborate summaries across different groups of data using `
 ```{r, eval = FALSE}
 # General format - Not the code!
 {data to use} %>% 
-   summarize({summary column name} = {operator(source column)},
-             {summary column name} = {operator(source column)}) 
+   summarize({summary column name} = {function(source column)},
+             {summary column name} = {function(source column)}) 
 ```
 </div>
 
@@ -234,7 +230,7 @@ You can also do more elaborate summaries across different groups of data using `
 ```{r, eval = FALSE}
 # General format - Not the code!
 {data to use} %>% 
-   summarize({summary column name} = {operator(source column)}) 
+   summarize({summary column name} = {function(source column)}) 
 ```
 </div>
 
@@ -291,10 +287,11 @@ summary(tb)
 
 ## Summary & Lab Part 1
 
-- summary stats (`mean()`) work with `pull()`
+- `pull()` creates a *vector*
 - don't forget the `na.rm = TRUE` argument!
 - `summary(x)`: quantile information
 - `summarize`: creates a summary table of columns of interest
+- summary stats (`mean()`) work with vectors or with `summarize()`
 
 🏠 [Class Website](https://jhudatascience.org/intro_to_r/)
 
@@ -306,6 +303,8 @@ summary(tb)
 Here we will be using the Youth Tobacco Survey data:
 http://jhudatascience.org/intro_to_r/data/Youth_Tobacco_Survey_YTS_Data.csv
 
+* Check out the data at: https://catalog.data.gov/dataset/youth-tobacco-survey-yts-data
+
 ```{r}
 yts <- read_csv("http://jhudatascience.org/intro_to_r/data/Youth_Tobacco_Survey_YTS_Data.csv")
 head(yts)
@@ -324,7 +323,7 @@ yts %>%
 
 ## How many `distinct()` values?
 
-`n_distinct()` tells you the number of unique elements. _Must pull the column first!_
+`n_distinct()` tells you the number of unique elements. It needs a vector so you _must pull the column first!_
 
 ```{r}
 yts %>%
@@ -338,7 +337,7 @@ options(max.print = 1000)
 ```
 
 
-## `dplyr`: `count` 
+## Use `count()` to return row count per category.
 
 Use `count` to return a frequency table of unique elements of a data.frame.
 
@@ -347,31 +346,33 @@ yts %>% count(LocationDesc)
 ```
 
 
-## `dplyr`: `count` 
-
-Multiple columns listed further subdivides the count.
+## Multiple columns listed further subdivides the `count()`
 
 ```{r, message = FALSE}
 yts %>% count(LocationDesc, TopicDesc)
 ```
 
+**Note:** `count()` includes NAs
 
-## `dplyr`: `count` 
-
-Multiple columns listed further subdivides the count.
+## GUT CHECK
 
-```{r, message = FALSE}
-yts %>% count(LocationDesc, TopicDesc)
-```
+The `count()` function can help us tally:
 
-<br>
+A. Sample size
 
-**Note:** `count()` includes NAs
+B. Rows per each category
 
+C. How many categories
 
 # Grouping
 
-## Perform Operations By Groups: dplyr
+## Goal 
+
+We want to find the average frequency that youth use tobacco products in the dataset.
+
+_How do we do this?_
+
+## Perform operations By groups: dplyr
 
 `group_by` allows you group the data set by variables/columns you specify:
 
@@ -381,7 +382,7 @@ yts
 ```
 
 
-## Perform Operations By Groups: dplyr
+## Perform operations by groups: dplyr
 
 `group_by` allows you group the data set by variables/columns you specify:
 
@@ -400,7 +401,7 @@ yts_grouped %>% summarize(avg_percent = mean(Data_Value, na.rm = TRUE))
 ```
 
 
-## Use the `pipe` to string these together!
+## Do it in one step: use `%>%` to string these together!
 
 Pipe `yts` into `group_by`, then pipe that into `summarize`:
 
@@ -474,20 +475,19 @@ yts %>%
 `count()` and `n()` can give very similar information.
 
 ```{r}
-mtcars %>% count(cyl)
-mtcars %>% group_by(cyl) %>% summarize(n()) # n() typically used with summarize
+yts %>% count(YEAR) %>% head(n = 3)
+yts %>% group_by(YEAR) %>% summarize(n = n()) %>% head(n = 3) # n() typically used with summarize
 ```
 
 
-# A few miscellaneous topics .. 
+# A few miscellaneous topics
 
 
 ## Base R functions you might see: `length` and `unique`
 
 These functions require a column as a vector using `pull()`.
 
 ```{r, message = FALSE}
-yts <- read_csv("http://jhudatascience.org/intro_to_r/data/Youth_Tobacco_Survey_YTS_Data.csv")
 yts_loc <- yts %>% pull(LocationDesc) # pull() to make a vector
 yts_loc %>% unique() # similar to distinct()
 ```
@@ -500,38 +500,26 @@ These functions require a column as a vector using `pull()`.
 yts_loc %>% unique() %>% length() # similar to n_distinct()
 ```
 
-## * New! * Many dplyr functions now have a `.by=` argument
-
-Pipe `yts` into `group_by`, then pipe that into `summarize`:
-
-```{r eval = FALSE}
-yts %>%
-  group_by(Response) %>%
-  summarize(avg_percent = mean(Data_Value, na.rm = TRUE),
-            max_percent = max(Data_Value, na.rm = TRUE))
-```
-
-is the same as..
-
-```{r eval = FALSE}
-yts %>%
-  summarize(avg_percent = mean(Data_Value, na.rm = TRUE),
-            max_percent = max(Data_Value, na.rm = TRUE),
-            .by = Response)
-```
-
-
 ## `summary()` vs. `summarize()`
 
 * `summary()` (base R) gives statistics table on a dataset. 
 * `summarize()` (dplyr) creates a more customized summary tibble/dataframe.
 
+## Functions you might also see
+
+* `rowwise`()`: functions will compute results for each row
+* `sum(!is.na())`: # of non-NAs in the data
+* `first()`: first value in the data
+* `last()`: last value in the data
+* `range()`: minimum and maximum of the data
+* `IQR()`: interquartile range of the data
+
 ## Summary & Lab Part 2
 
 - `count(x)`: what unique values do you have? 
   - `distinct()`: what are the distinct values?
   - `n_distinct()` with `pull()`: how many distinct values?
-- `group_by()`: changes all subsequent functions
+- `group_by()`: changes subsequent functions (remove with `ungroup()`)
   - combine with `summarize()` to get statistics per group
   - combine with `mutate()` to add column
 - `summarize()` with `n()` gives the count (NAs included) 
@@ -540,7 +528,7 @@ yts %>%
 
 💻 [Lab](https://jhudatascience.org/intro_to_r/modules/Data_Summarization/lab/Data_Summarization_Lab.Rmd)
 
-```{r, fig.alt="The End", out.width = "50%", echo = FALSE, fig.align='center'}
+```{r, fig.alt="The End", out.width = "20%", echo = FALSE, fig.align='center'}
 knitr::include_graphics(here::here("images/the-end-g23b994289_1280.jpg"))
 ```
 
@@ -592,3 +580,23 @@ tb %>%
 tb %>%
   summarize(across(starts_with("year"), ~mean(.x, na.rm = TRUE)))
 ```
+
+## * New! * Many dplyr functions now have a `.by=` argument
+
+Pipe `yts` into `group_by`, then pipe that into `summarize`:
+
+```{r eval = FALSE}
+yts %>%
+  group_by(Response) %>%
+  summarize(avg_percent = mean(Data_Value, na.rm = TRUE),
+            max_percent = max(Data_Value, na.rm = TRUE))
+```
+
+is the same as..
+
+```{r eval = FALSE}
+yts %>%
+  summarize(avg_percent = mean(Data_Value, na.rm = TRUE),
+            max_percent = max(Data_Value, na.rm = TRUE),
+            .by = Response)
+```

modules/Data_Summarization/lab/Data_Summarization_Lab.Rmd

@@ -26,7 +26,7 @@ bike <- read_csv(file = "http://jhudatascience.org/intro_to_r/data/Bike_Lanes.cs
 
 ### 1.1 
 
-How many bike "lanes" are currently in Baltimore?  You can assume each observation/row is a different bike "lane".  (hint: how do you get the number of rows of a data set? You can use `dim()` or `nrow()` or another function).
+How many streets with designated bike lanes are currently in Baltimore? You can assume each observation/row is a different street with one or more bike lanes. (Hint: how do you get the number of rows of a data set? You can use `dim()` or `nrow()` or another function).
 
 ```{r 1.1response}
 
@@ -47,7 +47,7 @@ Summarize the data to get the `max` of `length` using the `summarize` function.
 ```
 # General format 
 DATA_TIBBLE %>% 
-    summarize(SUMMARY_COLUMN_NAME = OPERATOR(SOURCE_COLUMN))
+    summarize(SUMMARY_COLUMN_NAME = FUNCTION(SOURCE_COLUMN))
 ```
 
 ```{r 1.3response}
@@ -61,8 +61,8 @@ Modify your code from 1.3 to add the `min` of `length` using the `summarize` fun
 ```
 # General format 
 DATA_TIBBLE %>% 
-    summarize(SUMMARY_COLUMN_NAME = OPERATOR(SOURCE_COLUMN),
-              SUMMARY_COLUMN_NAME = OPERATOR(SOURCE_COLUMN)
+    summarize(SUMMARY_COLUMN_NAME = FUNCTION(SOURCE_COLUMN),
+              SUMMARY_COLUMN_NAME = FUNCTION(SOURCE_COLUMN)
     )
 ```
 
@@ -80,8 +80,8 @@ Summarize the `bike` data to get the mean of `length` and `dateInstalled`. Make
 ```
 # General format 
 DATA_TIBBLE %>% 
-    summarize(SUMMARY_COLUMN_NAME = OPERATOR(SOURCE_COLUMN, na.rm = TRUE),
-              SUMMARY_COLUMN_NAME = OPERATOR(SOURCE_COLUMN, na.rm = TRUE)
+    summarize(SUMMARY_COLUMN_NAME = FUNCTION(SOURCE_COLUMN, na.rm = TRUE),
+              SUMMARY_COLUMN_NAME = FUNCTION(SOURCE_COLUMN, na.rm = TRUE)
     )
 ```