title: dplyr::select Object not found in self-made function
body: <p>I am trying to learn how to use functions to make my code easier to read and to recall. I am practicing on a function that is expected to subset my data with <code>filter()</code> (according to one of the function argument), keeping only part of the columns of the data I feed to the function with <code>select()</code> and plot the trend of an index over time with <code>ggplot() + geom_line()</code>.</p>
  
  <p>I found several related questions, but I could not solve the problem with any of them. I think my issue relates to the way I include the arguments within the function itself. Since I am quite new to writing functions in R (and, to some extent, to R itself), I would like to understand what I am missing.</p>
  
  <p>Below, a sample of my data obtained with <code>dput()</code>: </p>
  
  <pre><code>structure(list(denominazione_regione = c("Abruzzo", "Abruzzo", 
  "Abruzzo", "Abruzzo", "Abruzzo", "Abruzzo", "Abruzzo", "Abruzzo", 
  "Abruzzo", "Abruzzo", "Basilicata", "Basilicata", "Basilicata", 
  "Basilicata", "Basilicata", "Basilicata", "Basilicata", "Basilicata", 
  "Basilicata", "Basilicata", "Calabria", "Calabria", "Calabria", 
  "Calabria", "Calabria", "Calabria", "Calabria", "Calabria", "Calabria", 
  "Calabria", "Campania", "Campania", "Campania", "Campania", "Campania", 
  "Campania", "Campania", "Campania", "Campania", "Campania", "Emilia-Romagna", 
  "Emilia-Romagna", "Emilia-Romagna", "Emilia-Romagna", "Emilia-Romagna", 
  "Emilia-Romagna", "Emilia-Romagna", "Emilia-Romagna", "Emilia-Romagna", 
  "Emilia-Romagna", "Friuli Venezia Giulia", "Friuli Venezia Giulia", 
  "Friuli Venezia Giulia", "Friuli Venezia Giulia", "Friuli Venezia Giulia", 
  "Friuli Venezia Giulia", "Friuli Venezia Giulia", "Friuli Venezia Giulia", 
  "Friuli Venezia Giulia", "Friuli Venezia Giulia", "Lazio", "Lazio", 
  "Lazio", "Lazio", "Lazio", "Lazio", "Lazio", "Lazio", "Lazio", 
  "Lazio", "Liguria", "Liguria", "Liguria", "Liguria", "Liguria", 
  "Liguria", "Liguria", "Liguria", "Liguria", "Liguria", "Lombardia", 
  "Lombardia", "Lombardia", "Lombardia", "Lombardia", "Lombardia", 
  "Lombardia", "Lombardia", "Lombardia", "Lombardia", "Marche", 
  "Marche", "Marche", "Marche", "Marche", "Marche", "Marche", "Marche", 
  "Marche", "Marche", "Molise", "Molise", "Molise", "Molise", "Molise", 
  "Molise", "Molise", "Molise", "Molise", "Molise", "P.A. Bolzano", 
  "P.A. Bolzano", "P.A. Bolzano", "P.A. Bolzano", "P.A. Bolzano", 
  "P.A. Bolzano", "P.A. Bolzano", "P.A. Bolzano", "P.A. Bolzano", 
  "P.A. Bolzano", "P.A. Trento", "P.A. Trento", "P.A. Trento", 
  "P.A. Trento", "P.A. Trento", "P.A. Trento", "P.A. Trento", "P.A. Trento", 
  "P.A. Trento", "P.A. Trento", "Piemonte", "Piemonte", "Piemonte", 
  "Piemonte", "Piemonte", "Piemonte", "Piemonte", "Piemonte", "Piemonte", 
  "Piemonte", "Puglia", "Puglia", "Puglia", "Puglia", "Puglia", 
  "Puglia", "Puglia", "Puglia", "Puglia", "Puglia", "Sardegna", 
  "Sardegna", "Sardegna", "Sardegna", "Sardegna", "Sardegna", "Sardegna", 
  "Sardegna", "Sardegna", "Sardegna", "Sicilia", "Sicilia", "Sicilia", 
  "Sicilia", "Sicilia", "Sicilia", "Sicilia", "Sicilia", "Sicilia", 
  "Sicilia", "Toscana", "Toscana", "Toscana", "Toscana", "Toscana", 
  "Toscana", "Toscana", "Toscana", "Toscana", "Toscana", "Umbria", 
  "Umbria", "Umbria", "Umbria", "Umbria", "Umbria", "Umbria", "Umbria", 
  "Umbria", "Umbria", "Valle d'Aosta", "Valle d'Aosta", "Valle d'Aosta", 
  "Valle d'Aosta", "Valle d'Aosta", "Valle d'Aosta", "Valle d'Aosta", 
  "Valle d'Aosta", "Valle d'Aosta", "Valle d'Aosta", "Veneto", 
  "Veneto", "Veneto", "Veneto", "Veneto", "Veneto", "Veneto", "Veneto", 
  "Veneto", "Veneto"), mese = c(4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 
  4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 
  4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 
  5, 5, 5, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 
  5, 5, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 3, 4, 4, 4, 
  4, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 5, 5, 4, 4, 4, 4, 4, 4, 
  4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 
  5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 
  5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 
  4, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 
  5, 5, 5, 5, 5, 5, 5, 5, 5, 5), giorno = c(13, 14, 15, 17, 18, 
  19, 20, 21, 22, 24, 2, 3, 5, 7, 8, 9, 10, 11, 12, 15, 3, 4, 5, 
  6, 7, 8, 9, 10, 11, 12, 4, 5, 6, 7, 8, 9, 10, 14, 15, 16, 14, 
  15, 16, 17, 18, 19, 20, 21, 22, 23, 8, 9, 10, 11, 12, 13, 14, 
  15, 16, 17, 22, 23, 24, 25, 26, 27, 28, 29, 4, 6, 4, 9, 10, 11, 
  12, 13, 14, 15, 16, 17, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 
  30, 31, 1, 2, 3, 4, 5, 6, 7, 8, 27, 1, 2, 3, 5, 6, 7, 19, 16, 
  17, 3, 4, 7, 8, 9, 10, 11, 5, 6, 17, 6, 9, 10, 11, 12, 13, 14, 
  15, 16, 17, 20, 22, 23, 25, 27, 29, 30, 2, 3, 17, 3, 4, 5, 15, 
  16, 17, 20, 21, 22, 23, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 
  4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 6, 9, 10, 11, 12, 13, 14, 15, 
  16, 17, 23, 24, 25, 26, 27, 28, 29, 31, 1, 2, 7, 8, 9, 10, 29, 
  30, 1, 2, 3, 4, 5, 6, 7, 8, 12, 13, 14, 15, 16, 17), indice_covid = c(0.000722977172570487, 
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  0.00120040745199511, 0.0012181362510992, 0.00123036198182824, 
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  14716.6217521341, 14692.328961306, 14705.0026481401, 14769.6826905103, 
  14597.6696367375, 14639.6948408, 14993.871113465, 14987.0692878061, 
  15202.0032400773, 15286.6775188485, 13562.5240475235, 13758.6297471818, 
  14021.7576885192, 13988.6166137682, 13799.4732041881, 13751.7527026863, 
  13766.2678000316, 13571.910060438, 13623.0779614024, 13655.3846995732, 
  3709.28719515099, 3663.770468982, 3821.5951582046, 3732.70198593756, 
  3749.35660560317, 3778.03816208134, 3855.68070346596, 3810.36811408214, 
  3820.42951574437, 3665.04005381276, 3335.56624585953, 3512.40456485421, 
  3740.2617672617, 3888.6891916591, 3461.08282215474, 3728.54412703095, 
  3446.18323547991, 3258.89579011162, 3257.60074199724, 3276.18490288943, 
  32348.8642996309, 33599.4870235032, 33210.484779231, 33958.2022804436, 
  32468.5316869857, 32641.9078779708, 32259.8982267784, 32091.6180955748, 
  32341.9966623645, 32470.5441332424, 1721.88218494195, 1743.47148672928, 
  1760.81697619303, 1785.43776756444, 1722.99460417864, 1736.77961832881, 
  1762.4300896669, 1780.11858361459, 1800.48266294519, 1809.31694906057
  )), row.names = c(NA, -210L), class = c("grouped_df", "tbl_df", 
  "tbl", "data.frame"), groups = structure(list(denominazione_regione = c("Abruzzo", 
  "Basilicata", "Calabria", "Campania", "Emilia-Romagna", "Friuli Venezia Giulia", 
  "Lazio", "Liguria", "Lombardia", "Marche", "Molise", "P.A. Bolzano", 
  "P.A. Trento", "Piemonte", "Puglia", "Sardegna", "Sicilia", "Toscana", 
  "Umbria", "Valle d'Aosta", "Veneto"), .rows = list(1:10, 11:20, 
      21:30, 31:40, 41:50, 51:60, 61:70, 71:80, 81:90, 91:100, 
      101:110, 111:120, 121:130, 131:140, 141:150, 151:160, 161:170, 
      171:180, 181:190, 191:200, 201:210)), row.names = c(NA, -21L
  ), class = c("tbl_df", "tbl", "data.frame"), .drop = TRUE))
  
  </code></pre>
  
  <p><strong>The function</strong>:</p>
  
  <p>The function I am practicing with has 3 arguments: the dataset (which I called <code>data.moving</code>) and 2 additional entries: one to subset the data according to the column <code>denominazione_regione</code>, the second to choose which index to be plotted over time (the <code>data.frame</code> I feed to the function has 3 possible indices)</p>
  
  <pre><code>plot_by_reg &lt;- function(df, reg, dato) {
  
    #d &lt;- 
      df %&gt;% 
      dplyr::filter(denominazione_regione == reg) %&gt;%
      dplyr::mutate(calendario = format(as.Date(paste(mese,giorno , sep = "-" )  , format = "%m-%d" ), "%m-%d")) %&gt;%
      dplyr::select(c(denominazione_regione, calendario, all_of(dato))) %&gt;%
      ggplot(aes(x=df$calendario, y=df$dato)) + #, group = 1)) +
      geom_line(aes(group = 1)) +
      theme_dark()
  }
  
  </code></pre>
  
  <p><strong>The Issues</strong>:</p>
  
  <p>When I call the function, R returns me the following error></p>
  
  <pre><code>plot_by_reg(df = data.moving, reg = "Toscana", dato = "indice_covid")
  Errore: geom_line requires the following missing aesthetics: x and y
  Run `rlang::last_error()` to see where the error occurred.
  </code></pre>
  
  <p>Conversely, if I change the <code>ggplot()</code> aesthetics to recall the function argument (included within quotes "" in the function call( I get a graph, where the line is horizontal and with no real value on the y axis</p>
  
  <pre><code>plot_by_reg &lt;- function(df, reg, dato) {
  
    #d &lt;- 
      df %&gt;% 
      dplyr::filter(denominazione_regione == reg) %&gt;%
      dplyr::mutate(calendario = format(as.Date(paste(mese,giorno , sep = "-" )  , format = "%m-%d" ), "%m-%d")) %&gt;%
      dplyr::select(c(denominazione_regione, calendario, all_of(dato))) #%&gt;%
      ggplot(aes(x = calendario, y = dato) + #, group = 1)) +
      geom_line(aes(group = 1)) +
      theme_dark()
  }
  
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/9W1b0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9W1b0.png" alt="enter image description here"></a></p>
  
  <p>Finally, if I modify the <code>plot_by_reg</code> removing the <code>ggplot()</code> part, the function works, printing a <code>data.frame</code> with 3 columns </p>
  
  <pre><code>
  plot_by_reg &lt;- function(df, reg, dato) {
  
    #d &lt;- 
      df %&gt;% 
      dplyr::filter(denominazione_regione == reg) %&gt;%
      dplyr::mutate(calendario = format(as.Date(paste(mese,giorno , sep = "-" )  , format = "%m-%d" ), "%m-%d")) %&gt;%
      dplyr::select(c(denominazione_regione, calendario, all_of(dato))) #%&gt;%
      #ggplot(aes(x=df$calendario, y=df$dato)) + #, group = 1)) +
      #geom_line(aes(group = 1)) +
      #theme_dark()
  }
  </code></pre>
  
  <p>I think the problem lies in the way I call the function's argument in within it, but as far as I tried to change it, I always find an error. For instance, if I try to pass the argument <code>dato</code>,  without "", R throws an error <code>Error in plot_by_reg(df = data.moving, reg = Toscana, dato = indice_covid) : object "indice_covid" not found</code> in the <code>select()</code> line, as it does not find the element <code>df$dato</code>. The same commands outside the function work perfectly. </p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I forgot to mention the feature of the machine I am working with:</p>
  
  <pre><code>Sys.info()
            sysname           release           version          nodename           machine             login 
          "Windows"          "10 x64"     "build 18362" "DESKTOP-7D7TTKL"          "x86-64"         "Filippo" 
               user    effective_user 
          "Filippo"         "Filippo" 
  
  R.version
                 _                           
  platform       x86_64-w64-mingw32          
  arch           x86_64                      
  os             mingw32                     
  system         x86_64, mingw32             
  status                                     
  major          3                           
  minor          6.2                         
  year           2019                        
  month          12                          
  day            12                          
  svn rev        77560                       
  language       R                           
  version.string R version 3.6.2 (2019-12-12)
  nickname       Dark and Stormy Night     
  
  library(tidyverse)
  -- Attaching packages --------------------------------------- tidyverse 1.3.0 --
  v ggplot2 3.3.0     v purrr   0.3.3
  v tibble  2.1.3     v dplyr   0.8.4
  v tidyr   1.0.2     v stringr 1.4.0
  v readr   1.3.1     v forcats 0.4.0
  -- Conflicts ------------------------------------------ tidyverse_conflicts() --
  x dplyr::filter() masks stats::filter()
  x dplyr::lag()    masks stats::lag()
  Warning messages:
  1: package ‘tidyverse’ was built under R version 3.6.3 
  2: package ‘ggplot2’ was built under R version 3.6.3 
  </code></pre>