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v4 answer keys

answer_key/00_Very_basics_of_R_coding_key.Rmd

@@ -1,80 +1,91 @@
----
-title: "Very basics of R coding"
-author: "Chenxin Li"
-date: "9/12/2020"
-output:
-  html_document:
-    toc: yes  
-  html_notebook:
-    number_sections: yes
-    toc: yes
-    toc_float: yes
----
-
-```{r setup, include=FALSE}
-knitr::opts_chunk$set(echo = TRUE)
-```
-
-```{r}
-library(dplyr)
-```
-
-# Exercise
-
-Today you have learned some basic syntax of R. Now it's time for you to practice.
-
-## Q1:
-
-1)  Insert a new code chunk
-2)  make this matrix
-
-| \| 1 \| 1 \| 2 \| 2 \|
-| \| 2 \| 2 \| 1 \| 2 \|
-| \| 2 \| 3 \| 3 \| 4 \|
-| \| 1 \| 2 \| 3 \| 4 \|
-
-and save it as an item called my_mat2
-
-\
-3. select the 1st and 3rd rows and the 1st, 2nd and 4th columns, and save it as an item.
-
-\
-4. take the square root for each member of my_mat2, then take log2(), and lastly find the maximum value. Use the pipe syntax.\
-The command for maximum is `max()`.
-
-```{r}
-my_mat2 <- rbind(
-  c(1, 1, 2, 2),
-  c(2, 2, 1, 2),
-  c(2, 3, 3, 4),
-  c(1, 2, 3, 4)
-)
-
-my_mat3 <- my_mat2[c(1,3), -3]
-my_mat3
-
-my_mat2 %>% 
-  sqrt() %>% 
-  log2() %>% 
-  max()
-
-```
-
-## Q2:
-
-1)  Insert a code chunk
-2)  Use the following info to make a data frame and save it as an item called grades.\
-    Adel got 85 on the exam, Bren got 83 and Cecil got 93. Their letter grades are B, B, and A, respectively.\
-3)  Pull out the column with the scores. Use the `$` syntax.
-
-```{r}
-grades <- data.frame(
-  name = c("Adel", "Bren", "Cecil"),
-  score = c(85, 83, 93),
-  grade = c("B", "B", "A")
-) 
-
-grades
-
-grades$score
-```
+---
+title: "Very basics of R coding"
+author: "Chenxin Li"
+date: "9/12/2020"
+output:
+  html_document:
+    toc: yes  
+  html_notebook:
+    number_sections: yes
+    toc: yes
+    toc_float: yes
+---
+
+```{r setup, include=FALSE}
+knitr::opts_chunk$set(echo = TRUE)
+```
+
+```{r}
+library(dplyr)
+```
+
+# Exercise
+
+Today you have learned some basic syntax of R. Now it's time for you to practice.
+
+## Q1:
+
+# Excerice
+
+Today you have learned some basic syntax of R.
+Now it's time for you to practice.
+
+## Q1:
+
+1.  Insert a new code chunk
+2.  Make this matrix
+
+| 1  | 1 | 2 | 2 |
+| 2  | 2 | 1 | 2 |
+| 2  | 3 | 3 | 4 |
+| 1  | 2 | 3 | 4 |
+
+and save it as an item called `my_mat2`.
+
+3. Select the 1st and 3rd rows and the 1st, 2nd and 4th columns, and save it as an item.
+
+4. Take the square root for each member of my_mat2, then take log2(), and lastly find the maximum value.
+Use the pipe syntax. The command for maximum is `max()`.
+
+
+
+```{r}
+my_mat2 <- rbind(
+  c(1, 1, 2, 2),
+  c(2, 2, 1, 2),
+  c(2, 3, 3, 4),
+  c(1, 2, 3, 4)
+)
+
+my_mat3 <- my_mat2[c(1,3), -3]
+my_mat3
+
+my_mat2 %>% 
+  sqrt() %>% 
+  log2() %>% 
+  max()
+
+```
+
+## Q2:
+
+1.  Use the following info to make a data frame and save it as an item called "grade".
+    Adel got 85 on the exam, Bren got 83, and Cecil got 93.
+    Their letter grades are B, B, and A, respectively.
+    (Hint: How many columns do you have to have?)
+
+2. Pull out the column with the scores.
+    Use the `$` syntax.
+
+
+```{r}
+grades <- data.frame(
+  name = c("Adel", "Bren", "Cecil"),
+  score = c(85, 83, 93),
+  grade = c("B", "B", "A")
+) 
+
+grades
+
+grades$score
+```