问如何使用ifelse和grepl在一个长字符串的列的基础上创建一个包含子字符串的新列？

EN

    1
    during a demonstration flight, a u.s. army flyer flown by orville wright nose-dived into the ground from a height of approximately 75 feet, killing lt. thomas e. selfridge who was a passenger. this was the first recorded airplane fatality in history. one of two propellers separated in flight, tearing loose the wires bracing the rudder and causing the loss of control of the aircraft. orville wright suffered broken ribs, pelvis and a leg. selfridge suffered a crushed skull and died a short time later.
    2
    first u.s. dirigible akron exploded just offshore at an altitude of 1,000 ft. during a test flight.
    3
    the first fatal airplane accident in canada occurred when american barnstormer, john m. bryant, california aviator was killed.
    4
    the airship flew into a thunderstorm and encountered a severe downdraft crashing 20 miles north of helgoland island into the sea. the ship broke in two and the control car immediately sank drowning its occupants.
    5
    hydrogen gas which was being vented was sucked into the forward engine and ignited causing the airship to explode and burn at 3,000 ft..
    6
    crashed into trees while attempting to land after being shot down by british and french aircraft.
    7
    exploded and burned near neuwerk island, when hydrogen gas, being vented, was ignited by lightning.
    8
    crashed near the black sea, cause unknown.
    9
    shot down by british aircraft crashing in flames.
    10
    shot down in flames by the british 39th home defence squadron.
    11
    crashed in a storm.
    12
    shot down by british anti-aircraft fire and aircraft and crashed into the north sea.
    13
    caught fire and crashed. 

    ac$sumnew = ifelse(grepl("missing & crashed",ac$Summary),"missing and crashed",
        ifelse(grepl("shot | crashed",ac$Summary),"shot down and crashed",
        ifelse(grepl("struck | lightening",ac$Summary),"struck by lightening and crashed",
         ifelse(grepl("struck | bird & crashed",ac$Summary),"struck by bird and crashed",
         ifelse(grepl("exploded | crashed",ac$Summary),"exploded and crashed",
         ifelse(grepl("engine | failure",ac$Summary),"engine failure",
         ifelse(grepl("fog | crashed",ac$Summary),"crashed due to heavy fog",
         ifelse(grepl("fire | crashed",ac$Summary),"caught fire and crashed",
         ifelse(grepl("shot",ac$Summary),"shot down",             
         ifelse(grepl("crashed",ac$Summary),"Crashed",
         ifelse(grepl("shot",ac$Summary),"Shot down",
         ifelse(grepl("disappeared",ac$Summary),"Disappeared",
         ifelse(grepl("struck | obstacle | crashed ",ac$Summary),"struck by obstacle and Crashed",
         ifelse(grepl("crashed",ac$Summary),"crashed",
         ifelse(grepl("exploded",ac$Summary),"exploded",
         ifelse(grepl("fire",ac$Summary),"caught fire","others"))))))))))))))))

1
others
2
exploded and crashed
3
others
4
others
5
engine failure
6
shot down and crashed
7
exploded and crashed
8
Crashed
9
shot down and crashed
10
shot down and crashed
11
Crashed
12
missing and crashed
13
missing and crashed
14
missing and crashed
15
Crashed
16
shot down and crashed
17
shot down and crashed