Taking the Grunfeld data, which is built-in in R, for example,
(1)How can I construct a dataset (or dataframe) that consists of the data
of all firms in 1951?
(2)How can I calculate the average capital in each form over the period
1951-1954?
What I can imagine is to categorize the data by firm, and then select the
data between 1951 and 1954 for each firm, but how can I do it?
Thanks,
Miao
Grunfeld data:
invest value capital firm year 317.6 3078.5 2.8 General Motors 1935
391.8 4661.7 52.6 General Motors 1936 410.6 5387.1 156.9 General Motors
1937 257.7 2792.2 209.2 General Motors 1938 330.8 4313.2 203.4 General
Motors 1939 461.2 4643.9 207.2 General Motors 1940 512 4551.2 255.2 General
Motors 1941 448 3244.1 303.7 General Motors 1942 499.6 4053.7 264.1 General
Motors 1943 547.5 4379.3 201.6 General Motors 1944 561.2 4840.9 265 General
Motors 1945 688.1 4900.9 402.2 General Motors 1946 568.9 3526.5 761.5 General
Motors 1947 529.2 3254.7 922.4 General Motors 1948 555.1 3700.2
1020.1 General
Motors 1949 642.9 3755.6 1099 General Motors 1950 755.9 4833 1207.7 General
Motors 1951 891.2 4924.9 1430.5 General Motors 1952 1304.4 6241.7
1777.3 General
Motors 1953 1486.7 5593.6 2226.3 General Motors 1954 209.9 1362.4 53.8 US
Steel 1935 355.3 1807.1 50.5 US Steel 1936 469.9 2676.3 118.1 US Steel
1937 262.3 1801.9 260.2 US Steel 1938 230.4 1957.3 312.7 US Steel 1939
361.6 2202.9 254.2 US Steel 1940
...........
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