Providing functions to read data files directly from loggers or instruments would be an endless tasks, as there are countless varieties of formats. Additionally, such a function already exists: readr::read_delim (Wickham et al. (2024)).

We provide here some guidelines and examples on how to use read_delim to prepare your raw data files for fluxible.

Checklists for inputs

The first function to use when processing ecosystem gas fluxes data with fluxible is flux_match, which require two inputs: row_conc and field_record.

Input `raw_conc`

The input raw_conc is the file with the gas concentration measured over time, typically the file exported by the logger or instrument.

Column that will be used in fluxible do not contain space or special characters;
A gas concentration column as numeric;
A column in datetime format (yyyy-mm-dd hh:mm:ss) corresponding to each concentration data points.

Input `field_record`

The input field_record is the file that is telling which sample or plot was measured when, and eventually providing other meta data, such as campaign, site, type of measurement and so on.

Column that will be used in fluxible do not contain space or special characters;
A column indicating the start of each measurement in datetime format (yyyy-mm-dd hh:mm:ss).

Note that the current version of flux_match does not support non fixed measurement length, indicating an end column instead of the measurement_length argument. But it is possible to mimic flux_match and directly start with flux_fitting (see below).

By-passing `flux_match`

The flux_match function only intends to attribute a unique flux_id to each measurement. Depending on your setup, this step might not be necessary. The flux_fitting function is the step after flux_match and its input should check the following points:

Column that will be used in fluxible do not contain space or special characters;
A gas concentration column as numeric;
A column in datetime format (yyyy-mm-dd hh:mm:ss) corresponding to each concentration data points;
A column with a unique ID for each measurements;
A column indicating the start of each measurement in datetime format (yyyy-mm-dd hh:mm:ss);
A column indicating the end of each measurement in datetime format (yyyy-mm-dd hh:mm:ss).

Importing a single file

In this example we will import the file 26124054001.#00, which is a text file extracted from a logger with the ad-hoc licensed software. The first thing to do when importing a file with read_delim is to open the file in a text editor to look at its structure.

Screenshot of the file 26124054001.#00 in a text editor. We can see that the 25th first rows should not be imported, and that it is comma separated with a dot as a decimal point.

We will read the file with read_delim, and then use rename and mutate (from the dplyr package ¹ (Wickham et al., 2023)) to transform the columns into what we want, and dmy and as_datetime from the lubridate package Grolemund and Wickham (2011) to get our datetime column in the right format:

library(tidyverse)
# readr is part of tidyverse, and since we will also use dplyr
# we might as well load tidyverse

raw_conc <- read_delim(
  "ex_data/26124054001.#00",
  delim = ",", # our file is comma separated
  skip = 25 # the first 25 rows are logger infos that we do not want to keep
)

# let's see
head(raw_conc)
#> # A tibble: 6 × 7
#>   Date      Time     Type  `CO2 (V)` `H2O (V)` `CO2_calc (ppm)` `H2O_calc (ppt)`
#>   <chr>     <time>   <chr>     <dbl>     <dbl>            <dbl>            <dbl>
#> 1 26.06.20… 12:40:56 Inte…      2.08    0.0004             416.            0.007
#> 2 26.06.20… 12:40:57 Inte…      2.09    0.0004             418.            0.008
#> 3 26.06.20… 12:40:58 Inte…      2.08    0.0004             416.            0.007
#> 4 26.06.20… 12:40:59 Inte…      2.08    0.0004             416.            0.008
#> 5 26.06.20… 12:41:00 Inte…      2.06    0.0004             412.            0.008
#> 6 26.06.20… 12:41:01 Inte…      2.08    0.0004             416.            0.007

Not too bad… but we are not quite there yet:

Some column names contain space;
Some columns are not needed, removing them will make things lighter for later: Type (nothing to do with the type of measurement, something from the logger), CO2 (V), H2O (V) (those two are the voltage input to the logger, not what we want), and H2O_calc (ppt) (that one was not calibrated for this campaign so better remove it to avoid confusion);
The Date and Time columns should be gathered in one and transformed in yyyy-mm-dd hh:mm:ss format.

library(lubridate) # lubridate is what you want to deal with datetime issues

raw_conc <- raw_conc |>
  rename(
    co2_conc = "CO2_calc (ppm)"
  ) |>
  mutate(
    Date = dmy(Date), # to transform the date as a yyyy-mm-dd format
    datetime = paste(Date, Time), # we paste date and time together
    datetime = as_datetime(datetime) # datetime instead of character
  ) |>
  select(datetime, co2_conc)

head(raw_conc) # Et voila!
#> # A tibble: 6 × 2
#>   datetime            co2_conc
#>   <dttm>                 <dbl>
#> 1 2020-06-26 12:40:56     416.
#> 2 2020-06-26 12:40:57     418.
#> 3 2020-06-26 12:40:58     416.
#> 4 2020-06-26 12:40:59     416.
#> 5 2020-06-26 12:41:00     412.
#> 6 2020-06-26 12:41:01     416.

Note that it is also possible to use the col_names and col_select arguments directly in read_delim, but it has a higher risk of errors.


raw_conc <- read_delim(
  "ex_data/26124054001.#00",
  delim = ",", # our file is comma separated
  skip = 26, # removing the first 25th row and the header
  col_select = c(1, 2, 6),
  col_names = c("date", "time", rep(NA, 3), "co2_conc", NA)
)
head(raw_conc)
#> # A tibble: 6 × 3
#>   date       time     co2_conc
#>   <chr>      <time>      <dbl>
#> 1 26.06.2020 12:40:56     416.
#> 2 26.06.2020 12:40:57     418.
#> 3 26.06.2020 12:40:58     416.
#> 4 26.06.2020 12:40:59     416.
#> 5 26.06.2020 12:41:00     412.
#> 6 26.06.2020 12:41:01     416.

Importing multiple files

Quite often a field campaign will result in several files, because the logger was restarted or other events. In this example we will read all the files in “ex_data/” that contains “CO2” in their names.

library(fs)

raw_conc <- dir_ls( #listing all the files
  "ex_data", # at location "ex_data"
  regexp = "*CO2*" # that contains "CO2" in their name
) |>
  map_dfr(
    read_csv, # we map read_csv on all the files
    na = c("#N/A", "Over") # "#N/A" and Over should be treated as NA
  ) |>
  rename(
    conc = "CO2 (ppm)",
    datetime = "Date/Time"
  ) |>
  mutate(
    datetime = dmy_hms(datetime)
  ) |>
  select(datetime, conc)

head(raw_conc)
#> # A tibble: 6 × 2
#>   datetime             conc
#>   <dttm>              <dbl>
#> 1 2021-06-04 16:12:42  480.
#> 2 2021-06-04 16:12:43  481.
#> 3 2021-06-04 16:12:44  480.
#> 4 2021-06-04 16:12:45  480.
#> 5 2021-06-04 16:12:46  480.
#> 6 2021-06-04 16:12:47  479.

The one file per flux approach

The Fluxible R package is designed to process data that were measured continuously (in a single or several files) and a field_record that records what was measured when. Another strategy while measuring gas fluxes on the field is to create a new file for each measurement, with the file name as the flux ID. The approach is similar to reading multiple files, except we add a column with the file name, and then can by-pass flux_match.

library(tidyverse)
library(lubridate)
library(fs)

raw_conc <- dir_ls( #listing all the files
  "ex_data/field_campaign" # at location "ex_data/field_campaign"
) |>
  map_dfr( # we map read_tsv on all the files
    read_tsv, # read_tsv is for tab separated value files
    skip = 3,
    id = "filename" # column with the filename, that we can use as flux ID
  ) |>
  rename( # a bit of renaming to make the columns more practical
    co2_conc = "CO2 (umol/mol)",
    h2o_conc = "H2O (mmol/mol)",
    air_temp = "Temperature (C)",
    pressure = "Pressure (kPa)"
  ) |>
  mutate(
    datetime = paste(Date, Time),
    datetime = as.POSIXct(
      datetime, format = "%Y-%m-%d %H:%M:%OS"
    ), # we get rid of the milliseconds
    pressure = pressure / 101.325, # conversion from kPa to atm
    filename = substr(filename, 24, 70) # removing folder names
  ) |>
  select(datetime, co2_conc, h2o_conc, air_temp, pressure, filename)

head(raw_conc)
#> # A tibble: 6 × 6
#>   datetime            co2_conc h2o_conc air_temp pressure filename              
#>   <dttm>                 <dbl>    <dbl>    <dbl>    <dbl> <chr>                 
#> 1 2023-12-14 10:57:01     416.     22.7     22.4    0.790 1_2000_east_1_day_a-2…
#> 2 2023-12-14 10:57:02     407.     22.5     22.4    0.791 1_2000_east_1_day_a-2…
#> 3 2023-12-14 10:57:03     404.     23.0     22.4    0.790 1_2000_east_1_day_a-2…
#> 4 2023-12-14 10:57:04     421.     22.6     22.3    0.790 1_2000_east_1_day_a-2…
#> 5 2023-12-14 10:57:05     411.     22.8     22.3    0.791 1_2000_east_1_day_a-2…
#> 6 2023-12-14 10:57:06     401.     23.0     22.3    0.790 1_2000_east_1_day_a-2…

The tricky one

What happens when you extract a logger file in csv using a computer with settings using comma as a decimal point (which is quite standard in Europe)? Well, you get a comma separated values (csv) file, with decimals separated by… comma.

Ideally the file should have been extracted in European csv, that is with comma for decimals and semi-colon as column separator. But here we are.

Screenshot of the file 011023001.#01 opened in a text editor. We can see that it is comma separated, but that the decimal point is also a comma. Additionally, we see that some variables were measured only every 10 seconds, meaning that each row has a different number of commas… Gnnnnnnn

Let’s try the usual way first:


raw_conc <- read_csv( # read_csv is the same as read_delim(delim = ",")
  "ex_data/011023001.#01",
  col_types = "Tcdddddd",
  na = "#N/A" # we tell read_csv what NA look like in that file
)

head(raw_conc)
#> # A tibble: 6 × 8
#>   `Date/Time` Type     `CO2_input (V)` `PAR_input (mV)` `Temp_air ('C)`
#>   <dttm>      <chr>              <dbl>            <dbl>           <dbl>
#> 1 NA          Interval               2               28               0
#> 2 NA          Interval               2               28              NA
#> 3 NA          Interval               2               28              NA
#> 4 NA          Interval               2               35              NA
#> 5 NA          Interval               2               31              NA
#> 6 NA          Interval               2               23              NA
#> # ℹ 3 more variables: `Temp_soil ('C)` <dbl>, `CO2 (ppm)` <dbl>,
#> #   `PAR (umolsm2)` <dbl>

It took the column names right, but then of course interpreted all comma as separators, and made a mess. Let’s see if we can skipped the header and then assemble the columns with left and right side of the decimal point:

raw_conc <- read_csv(
  "ex_data/011023001.#01",
  skip = 1, # this time we skip the row with the column names
  col_names = FALSE, # and we tell read_csv that we do not provide column names
  na = "#N/A" # we tell read_csv what NA look like in that file
)

head(raw_conc)
#> # A tibble: 6 × 14
#>   X1     X2       X3 X4       X5 X6       X7 X8    X9      X10   X11 X12     X13
#>   <chr>  <chr> <dbl> <chr> <dbl> <chr> <dbl> <chr> <chr> <dbl> <dbl> <chr> <dbl>
#> 1 01.10… Inte…     2 0028      0 0806…    12 00    10       81   400 "55"     20
#> 2 01.10… Inte…     2 0028     NA <NA>     NA 400   56       NA    NA ""       NA
#> 3 01.10… Inte…     2 0028     NA <NA>     NA 400   55       NA    NA ""       NA
#> 4 01.10… Inte…     2 0035     NA <NA>     NA 400   70       NA    NA ""       NA
#> 5 01.10… Inte…     2 0031     NA <NA>     NA 400   61       NA    NA ""       NA
#> 6 01.10… Inte…     2 0023     NA <NA>     NA 400   45       NA    NA ""       NA
#> # ℹ 1 more variable: X14 <chr>

The problem now is that CO2 concentration was measured every second (with a comma!), while other variable were measured every 10 seconds. That means every 10th row has 14 comma separated elements, while the others have only 10. Uhhhhhhhhh

At this point, you might want to get the field computer out again and reprocess your raw file with a european csv output, or anything that is not comma separated, or set the decimal point as a… point. But for the sake of it, let’s pretend that it is not an option and solve that issue in R:

# we read each row of our file as an element of a list
list <- readLines("ex_data/011023001.#01")
list <- list[-1] # removing the first element with the column names

# we first deal with the elements where we have those environmental data
# that were measured every 10 seconds
listenv <- list[seq(1, length(list), 10)]
env_df <- read.csv(
  textConnection(listenv), # we read the list into a csv
  header = FALSE, # there is no header
  colClasses = rep("character", 14)
  # specifying that those columns are character is important
  # if read as integer, 06 becomes 6, and when putting columns together,
  # 400.06 will be read as 400.6, which is wrong
)

env_df <- env_df |>
  mutate(
    datetime = dmy_hms(V1),
    temp_air = paste(
      V7, # V7 contains the left side of the decimal point
      V8, # V8 the right side
      sep = "." # this time we put it in american format
    ),
    temp_air = as.double(temp_air), # now we can make it a double
    temp_soil = as.double(paste(V9, V10, sep = ".")),
    co2_conc = as.double(paste(V11, V12, sep = ".")),
    PAR = as.double(paste(V13, V14, sep = "."))
  ) |>
  select(datetime, temp_air, temp_soil, co2_conc, PAR)

# now we do the same with the other elements of the list
list_other <- list[-seq(1, length(list), 10)]
other_df <- read.csv(
  textConnection(list_other),
  header = FALSE,
  colClasses = rep("character", 10)
)

other_df <- other_df  |>
  mutate(
    datetime = dmy_hms(V1),
    co2_conc = as.double(paste(V8, V9, sep = "."))
  ) |>
  select(datetime, co2_conc)

# and finally we do a full join with both
conc_df <- full_join(env_df, other_df, by = c("datetime", "co2_conc")) |>
  arrange(datetime) # I like my dataframes in chronological order
head(conc_df)
#>              datetime temp_air temp_soil co2_conc  PAR
#> 1 2023-10-01 11:23:40       12     10.81   400.55 20.6
#> 2 2023-10-01 11:23:41       NA        NA   400.56   NA
#> 3 2023-10-01 11:23:42       NA        NA   400.55   NA
#> 4 2023-10-01 11:23:43       NA        NA   400.70   NA
#> 5 2023-10-01 11:23:44       NA        NA   400.61   NA
#> 6 2023-10-01 11:23:45       NA        NA   400.45   NA

That was a strange mix of tidyverse and base R, and I would definitely try to do some plots to check if the data are making sense (number around 420 are most likely CO₂ concentration, those between 5 and 20 probably temperature, and soil temperature should be lower than air temperature). But it worked…

Grolemund, G. and Wickham, H. (2011), “Dates and times made easy with lubridate”, Journal of Statistical Software, Vol. 40 No. 3, pp. 1–25.

Wickham, H., Averick, M., Bryan, J., Chang, W., McGowan, L.D., François, R., Grolemund, G., et al. (2019), “Welcome to the tidyverse”, Journal of Open Source Software, Vol. 4 No. 43, p. 1686.

Wickham, H., François, R., Henry, L., Müller, K. and Vaughan, D. (2023), Dplyr: A Grammar of Data Manipulation, Manual,.

Wickham, H., Hester, J. and Bryan, J. (2024), Readr: Read Rectangular Text Data, Manual,.

both dplyr and readr are part of the tidyverse (Wickham et al., 2019).↩︎

Preparing the data for fluxible