Below is sample data that I have for two assets, I have 35 assets with varying start times to when data is available to be analyzed for. I had 35 separate .csv files and I have read them all into my environment and have combined them into 1 data frame in R that looks the the following sample data below: (Most assets have daily data, the start times to when the data is available is what varies, I subset the data to reduce the amount of records to provide an examples of what I am trying to achieve.

time          close        asset      dchange       month      year
2020-05-22    0.8230766    Celo       198.2538837     5        2020
2020-05-23    2.4585544    Celo      -19.85613825     5        2020
...
2020-05-31    1.4844532    Celo       6.02260537      5        2020
...
2020-12-01    1.9900000    Celo       5.98348954      12       2020               
2020-12-31    2.0100000    Celo       1.00502513      12       2020                                                         



2019-09-01    0.08976233   HBAR       -3.350752111    9        2019
2019-09-02    0.08675461   HBAR      -19.85613825     9        2019
...
2019-09-30    0.03794833   HBAR       2.650509119     9        2019
...
2019-12-01    0.8092034    HBAR       5.98348954      12       2019                
2019-12-31    1.2100000    HBAR       1.00502513      12       2019                

  "time" is the date of the the asset 
  "close" is the close price of the the asset 
  "asset" is the name of the asset
  "dchange" is the daily percent change of the asset from current day to the previous day
  "month" is the month in a numerical value
  "year" is the year in a numerical value 


I am trying to add two new columns that will calculate the following: 

 - Percentage change of the asset for the month & year combination (using earliest month data available and latest month data)
 - Percentage change of the asset for the year (using earliest year data available to latest year data for the same year)

I am aiming for the following output:

time          close        asset      dchange       month      year    monthly change  yearly change                                                    4
2020-05-22    0.8230766    Celo       198.2538837     5        2020        80.35       144.20  
2020-05-23    2.4585544    Celo      -19.85613825     5        2020        80.35       144.20
...
2020-05-31    1.4844532    Celo       6.02260537      5        2020        80.35       144.20
...
2020-12-01    1.9900000    Celo       5.98348954      12       2020        5.08        144.20
2020-12-31    2.0100000    Celo       1.00502513      12       2020        5.08        144.20                                               144.20   


2019-09-01    0.08976233   HBAR      -3.350752111     9        2019       -57.23        1248
2019-09-02    0.08675461   HBAR      -19.85613825     9        2019       -57.23        1248
...
2019-09-30    0.03794833   HBAR       2.650509119     9        2019       -57.23        1248
...
2019-12-01    0.8092034    HBAR       5.98348954      12       2019        49.52        1248
2019-12-31    1.2100000    HBAR       1.00502513      12       2019        49.52        1248                                               1248   

I was able to conduct some research to understand I may be able to use monthlyReturn-function from quantmod, not sure if I should use this in conjunction with lapply? I would appreciate any help with trying to get the desired results.