count number of times string appears in a column - r

Question

Can you think about an intuitive way of calculating the number of times the word space appears in a certain column? Or any other solution that is viable.
I basically want to know how many times the space key was pressed, however some participants made the mistake and pressed other keys which would also be considered a mistake. So I was wondering if I should go with the "key_resp.rt" column instead and count the number of response times instead. If you had any idea of how to do both it would be great as I may need to use both.
I used the following code but the results do not conform to the data.
Data %>% group_by(Participant, Session) %>% summarise(false_start = sum(str_count(key_resp.keys, "space")))
Here is a snippet of my data:
Participant RT Session key_resp.keys key_resp.rt
X 0.431265 1 ["space"] [2.3173399999941466]
X 0.217685 1
X 0.317435 2 ["space","space"] [0.6671900000001187,2.032510000000002] 2020.1.3 4
Y 0.252515 1
Y 0.05127 2 ["space","space","space","space","space","space","space","space","space"] [4.917419999999765,6.151149999999689,6.333714999999771,6.638249999999971,6.833514999999338,7.0362499999992,7.217724999999504,7.38576999999988,7.66913999999997]
dput(droplevels(head(Data_PVT)))
structure(list(Interval_stimulus = c(4.157783411, 4.876139922,
5.67011868, 9.338167417, 9.196342656, 7.62448411), Participant = structure(c(1L,
1L, 1L, 1L, 1L, 1L), .Label = "ADH80254", class = "factor"),
RT = c(431.265, 277.99, 253.515, 310.53, 299.165, 539.46),
Session = c(1L, 1L, 1L, 1L, 1L, 1L), date = structure(c(1L,
1L, 1L, 1L, 1L, 1L), .Label = "2020-06-12_11h11.47.141", class = "factor"),
key_resp.keys = structure(c(2L, 1L, 1L, 1L, 1L, 1L), .Label = c("",
"[\"space\"]"), class = "factor"), key_resp.rt = structure(c(2L,
1L, 1L, 1L, 1L, 1L), .Label = c("", "[2.3173399999941466]"
), class = "factor"), psychopyVersion = structure(c(1L, 1L,
1L, 1L, 1L, 1L), .Label = "2020.1.3", class = "factor"),
Trials = 0:5, Reciprocal = c(2.31875992719094, 3.59725169970143,
3.94453977082224, 3.22030077609249, 3.3426370063343, 1.85370555740926
)), row.names = c(NA, 6L), class = "data.frame")
Expected output:
Participant Session false_start
x 1 0
x 2 1
y 1 2
y 2 1
z 1 10
z 2 3

Answer 1

We can use str_count to count "space" values for each Participant and Session and sum them to get total. For all_false_start we count number of words in it.
library(dplyr)
library(stringr)
df %>%
group_by(Participant, Session) %>%
summarise(false_start = sum(str_count(key_resp.keys, '\\bspace\\b')),
all_false_start = sum(str_count(key_resp.keys, '\\b\\w+\\b')))