R Shiny App for Data Visualization

Question

I am trying to create a R shiny App for my data visualization. The data looks like

ID  route_id    trip_id direction   boarding    alighting   load
192197  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  68  0   167
192198  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  4   0   171
192199  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  4   0   175
192200  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  1   0   176
192201  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  3   0   179
192202  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  9   0   188
192203  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  0   0   188
192204  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  1   0   189
192205  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  1   0   190
192206  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  0   0   190
192207  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  1   0   191
192208  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  0   0   191
192209  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  4   0   195
192210  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  0   0   195
192211  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  3   0   198
192212  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  14  0   212
192213  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  0   23  189
192214  760-76  8223726-MAR15-MVS-BUS-Weekday-01    Southbound_760__Express_/_Downtown  0   27  162
194205  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   15  0   154
194206  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   0   154
194207  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   0   154
194208  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   0   154
194209  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   0   154
194210  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   0   154
194211  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   0   154
194212  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   15  0   169
194213  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   0   165
194214  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   1   4   166
194215  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   0   166
194216  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   1   0   167
194217  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   3   0   170
194218  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   7   163
194219  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   2   161
194220  589-76  8224010-MAR15-MVS-BUS-Weekday-01    Northbound_589__Express_/_Minneapolis   0   9   152
313432  852-76  8227043-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 21  0   151
313433  852-76  8227043-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 0   0   151
313434  852-76  8227043-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 0   0   151
313435  852-76  8227043-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 6   0   157
313616  852-76  8227045-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 53  0   183
313617  852-76  8227045-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 0   0   183
313618  852-76  8227045-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 0   0   183
313619  852-76  8227045-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 9   0   192
313620  852-76  8227045-MAR15-MVS-BUS-Weekday-01    Southbound_852__Express_/_Northtown_/_Dntn_Mpls 0   24  168
325301  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    18  0   160
325302  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    2   0   162
325303  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    0   0   162
325304  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    6   7   161
325305  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    6   2   165
325306  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    5   2   168
325307  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    18  12  174
325308  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    4   5   169
325309  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    0   4   169
325310  21-76   8227241-MAR15-MVS-BUS-Weekday-01    Westbound_21__Selby-Lake/_Uptown    0   0   169
352204  94-76   8227923-MAR15-MVS-BUS-Weekday-01    Westbound_94_Express_/_Downtown_/_Minneapolis   55  0   155
352398  94-76   8227934-MAR15-MVS-BUS-Weekday-01    Westbound_94_Express_/_Downtown_/_Minneapolis   52  0   170
352399  94-76   8227934-MAR15-MVS-BUS-Weekday-01    Westbound_94_Express_/_Downtown_/_Minneapolis   0   11  159
352400  94-76   8227934-MAR15-MVS-BUS-Weekday-01    Westbound_94_Express_/_Downtown_/_Minneapolis   0   2   157
352674  94-76   8227949-MAR15-MVS-BUS-Weekday-01    Westbound_94_Express_/_Downtown_/_Minneapolis   37  0   162
352675  94-76   8227949-MAR15-MVS-BUS-Weekday-01    Westbound_94_Express_/_Downtown_/_Minneapolis   0   10  152
390699  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 48  1   164
390700  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 2   0   166
390701  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 3   0   169
390702  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 3   1   171
390703  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   171
390704  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 4   0   175
390705  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 16  0   191
390706  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   191
390707  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 12  0   203
390708  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 1   0   204
390709  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 4   11  197
390710  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   197
390711  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 7   4   200
390712  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 1   3   198
390713  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   1   197
390714  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   187
390715  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 6   10  193
390716  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 2   1   194
390717  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   194
390718  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   2   184
390719  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   8   184
390720  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   9   175
390721  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 1   0   176
390722  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   176
390723  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 3   4   165
390724  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   10  165
390725  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   2   163
390726  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   2   161
390727  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   2   159
390728  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   159
390729  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   3   153
390730  22-76   8270934-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   3   153
390817  22-76   8270935-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 11  0   158
390818  22-76   8270935-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   158
390819  22-76   8270935-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   158
390820  22-76   8270935-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   158
390821  22-76   8270935-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 2   0   160
390822  22-76   8270935-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   160
390823  22-76   8270935-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   160
392402  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 20  0   170
392403  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   170
392404  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   8   162
392405  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   162
392406  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   3   159
392407  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   159
392408  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   159
392409  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   152
392410  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   7   152
392411  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   152
392412  22-76   8270947-MAR15-MVS-BUS-Weekday-01    Southbound_22H__Cedar-28Av/VA_Med_Ctr/Via_Dupont-57 0   0   152
415001  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  27  0   169
415002  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  0   0   169
415003  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  0   5   164
415004  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  3   0   167
415005  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  0   0   167
415006  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  0   0   167
415007  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  0   0   167
415008  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  0   0   167
415009  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  0   0   166
415010  17-76   8339808-MAR15-MVS-BUS-Weekday-01    Eastbound_17__Downtown  0   1   166
422541  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  35  0   160
422542  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  0   1   159
422543  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  2   0   161
422544  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  34  0   195
422545  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  3   0   198
422546  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  2   5   195
422547  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  0   6   189
422548  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  1   0   190
422549  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  1   3   188
422550  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  0   0   187
422551  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  0   1   187
422552  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  0   1   184
422553  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  2   2   186
422554  17-76   8339910-MAR15-MVS-BUS-Weekday-01    Eastbound_17W__Wash_St_NE_/_To_27th_NE  0   30  156
441158  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 49  0   153
441159  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 5   0   158
441160  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   158
441161  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 3   0   161
441162  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   161
441163  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   161
441164  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 1   0   162
441165  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   162
441166  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   162
441167  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   162
441168  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   162
441169  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   162
441170  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   162
441171  724-76  8346221-MAR15-MVS-BUS-Weekday-01    Southbound_724_Brklyn_Ctr_/_Transit_Ctr 0   0   162

So the following is my ui.R The file takes input from the user for route_id, and then creatw bar graph for eg. load for various stop_id.

ui <- fluidPage(
  pageWithSidebar(
    headerPanel('FAST_TRIPS Visulization', windowTitle = "Fast_trips Visaualization"),
    sidebarPanel(
      selectInput('route', 'Choose the Route No.', unique(y['route_id'])),
      selectInput('id', 'Please Choose Stop or Trip ID', c('stop_id','trip_id')),
      selectInput('rider', 'What do you wanna compare?', c('boarding', 'alighting', 'load')),
      radioButtons('method','Please select your method', c('Sum', 'Average'))),
    mainPanel(

      plotOutput('plot1')

    )
  )
)

and my server.R is follwing

server <- function(input, output, session) {

  # Combine the selected variables into a new data frame



  selectedData <- reactive({
    y[c('route_id', input$id, input$rider)]

  })

  data <- reactive({
    subset(selectedData(), route_id == input$route)
  })


  a <- reactive({
    aggregate(input$rider~input$id,data,sum)
  })



  output$plot1 <- renderPlot({barplot(a[input$rider])})

}

Every time I run this app. i get the following error:

object of type 'closure' is not subsettable

I am new in creating R shiny app. Please help

Answer 1

Try rewriting server.R in the following way:

server <- function(input, output, session) {
  # Combine the selected variables into a new data frame
  data <- reactive({
    subset(y, route_id == input$route, 
        select = c('route_id', input$id, input$rider))
  })
  a <- reactive({
    aggregate(as.formula(paste0(input$rider, "~", input$id)), data(), sum)
  })  
  output$plot1 <- renderPlot({
    barplot(a()[,input$rider])
  })
}

---

Explanation. There are several problems with the code, but as far as I can tell, the problem that gives rise to your error message is that you did not specify your reactive functions (e.g. data, a) with parentheses, e.g. in your calls to aggregate and barplot.

Another error is that you call aggregate using the formula construct, but input$rider~input$id is actually something like "boarding"~"trip_id", rather than boarding~trip_id. I amended this using as.formula(paste0(...)).

Third, barplot takes a vector or matrix for its height argument, but using a()[input$rider] gives you a dataframe; instead, use a()[, input$rider] (with the comma).

Fourth, in your ui.R, you have a stop_id option, but this column doesn't actually exist in your dataframe. I didn't change it since it produces a warning but does not kill your app.

Fifth, note that you can filter and select columns with a single call to subset.

You should get an output like this: