What is the equivalent of python's idxmin() in R?

Question

I often have situations where I have to find the first instance of a value in a table. For example, below I have to find the color of the first instance of each candy_type ordered by sequence:

d = {'candy_type':['A','A','B','B','C','C','C'],'sequence':[2,1,1,2,2,3,1], 'color':['Red','Black','Green','Yellow','Orange','White','Purple']}
df = pd.DataFrame(data=d)
df
+----+--------------+------------+---------+
|    | candy_type   |   sequence | color   |
|----+--------------+------------+---------|
|  0 | A            |          2 | Red     |
|  1 | A            |          1 | Black   |
|  2 | B            |          1 | Green   |
|  3 | B            |          2 | Yellow  |
|  4 | C            |          2 | Orange  |
|  5 | C            |          3 | White   |
|  6 | C            |          1 | Purple  |
+----+--------------+------------+---------+
#sort the dataframe by each candy_type's sequence and reset the index
df_sorted = df.sort_values(['candy_type','sequence']).reset_index(drop=True)

#make the index into a column
df_sorted_index = df_sorted.reset_index(drop=False)

df_sorted_index
+----+---------+--------------+------------+---------+
|    |   index | candy_type   |   sequence | color   |
|----+---------+--------------+------------+---------|
|  0 |       0 | A            |          1 | Black   |
|  1 |       1 | A            |          2 | Red     |
|  2 |       2 | B            |          1 | Green   |
|  3 |       3 | B            |          2 | Yellow  |
|  4 |       4 | C            |          1 | Purple  |
|  5 |       5 | C            |          2 | Orange  |
|  6 |       6 | C            |          3 | White   |
+----+---------+--------------+------------+---------+

#find the first instance of each candy type; show the whole row 
df_sorted_index.loc[df_sorted_index.groupby('candy_type')['index'].idxmin()]
+----+---------+--------------+------------+---------+
|    |   index | candy_type   |   sequence | color   |
|----+---------+--------------+------------+---------|
|  0 |       0 | A            |          1 | Black   |
|  2 |       2 | B            |          1 | Green   |
|  4 |       4 | C            |          1 | Purple  |
+----+---------+--------------+------------+---------+

Answer 1

You can use match :

## Create sorted data.frame
d <- data.frame(
  candy_type = c('A','A','B','B','C','C','C'),
  sequence = c(2,1,1,2,2,3,1),
  color = c('Red','Black','Green','Yellow','Orange','White','Purple')
)
d <- d[order(d[["candy_type"]], d[["sequence"]]), ]

## Works when candy_type is a factor column
## Otherwise, use unique() instead of levels()
first_of_type <- match(levels(d[["candy_type"]]), d[["candy_type"]])
first_of_type
# [1] 1 3 5

d[first_of_type, ]
#   candy_type sequence  color
# 2          A        1  Black
# 3          B        1  Green
# 7          C        1 Purple

Answer 2

which.min() is R's the equivalent of idxmin(). Both find the minimum value in an array and return the index of the first such value - useful if there are ties.