title: ggplot2 strip text labels facet_wrap
body: <p>I have searched other posts on this topic but can't figure out my problem. I have budgetary data on Brazilian government agencies, and have a classification of agency types. To produce my plot, I do this:  </p>
  
  <pre><code>g &lt;- ggplot(data=totalex.df, aes(x=year, y=totalex.billions))
  
  g + 
  geom_line(aes(colour=factor(agency.type))) + 
  facet_wrap(agency.type ~  unit, ncol=6) + 
  opts(strip.text.x = theme_text(size=2)) + 
  opts(axis.text.x=theme_text(size=4)) + 
  opts(legend.position="none") + 
  scale_y_sqrt("total expenditure (billions)")
  </code></pre>
  
  <p>My problem is, my facet labels now contain two pieces of information: the agency type and the name of the unit--<a href="https://dl.dropbox.com/u/4210336/sqrt_expenditure.pdf" rel="nofollow">this is a pdf of the graph</a> produced with the above code. I only want it to contain the name of the unit. However, if I drop the agency.type from the facet_wrap command, ggplot loses the order of the agencies. </p>
  
  <p>The output of <code>dput(totalex.df)</code> is quite long but here it is for the first 100 observations</p>
  
  <pre><code>&gt; dput(totalex.df.short)
  structure(list(year = c(2006, 2006, 2006, 2006, 2006, 2006, 2006, 
  2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 
  2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 
  2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 
  2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 
  2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 
  2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2006, 2007, 2007, 
  2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 
  2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 2007, 
  2007, 2007, 2007, 2007, 2007), totalex = c(312685301, 46492724, 
  85210069, 1478565787, 193941282, 260659307, 8327549603, 0, 18474604, 
  91006939, 53538760, 91800981, 402711174, 1290377603, 978348209, 
  48360776, 24676283, 89820385, 1038592122, 5364674136, 127383506, 
  7552311, 3847705355, 232732854, 34317692, 351714802, 156996087, 
  104782402, 0, 47741444, 475303761, 229743044, 102577783, 19106706, 
  78619935, 0, 730381485, 998733938, 110785185, 37114540, 108530853, 
  0, 0, 0, 2660417864, 169144966, 104350391, 1038914804, 336660855, 
  11995616, 0, 0, 9085111, 0, 5281402, 138708048, 11283655, 478421026, 
  221976619, 95680527, 8270558, 890375094, 0, 156563720, 198830207, 
  286909569, 5525428151, 734738984, 218905808, 1120014693, 859180, 
  359873525, 50214197, 95572929, 1628550454, 227051722, 286610734, 
  8868199792, 17388668, 19551190, 101047436, 58123546, 101878908, 
  423760647, 1019623567, 1061465081, 49559379, 24278026, 110344326, 
  1145862548, 7610896352, 163919333, 8376104, 4355447941, 282679957, 
  45506963, 392551882, 208594544, 122420822, 0), agency.type = structure(c(NA, 
  NA, NA, 3L, 1L, 1L, 7L, 1L, 1L, 1L, 1L, 1L, 4L, 1L, 1L, 1L, 1L, 
  3L, 1L, 6L, 1L, 1L, 7L, 1L, 3L, 3L, 1L, 3L, 1L, 1L, 1L, 3L, 3L, 
  1L, 3L, 1L, 1L, 1L, 3L, 3L, 3L, 1L, 5L, 3L, 1L, 5L, 3L, 1L, 1L, 
  1L, 1L, 3L, 3L, 3L, 1L, 1L, 1L, 1L, 3L, 1L, 1L, 4L, 1L, 1L, 2L, 
  1L, 1L, 3L, 1L, 1L, 3L, NA, NA, NA, 3L, 1L, 1L, 7L, 1L, 1L, 1L, 
  1L, 1L, 4L, 1L, 1L, 1L, 1L, 3L, 1L, 6L, 1L, 1L, 7L, 1L, 3L, 3L, 
  1L, 3L, 1L), .Label = c("Delivery", "Guidance for policy formulation / Research", 
  "Regulatory", "Regulatory / Delivery", "Regulatory/Delivery", 
  "Transfer / delivery", "Transfer/Regulatory/Deliver"), class = "factor"), 
      unit = structure(c(29L, 28L, 27L, 17L, 21L, 66L, 55L, 5L, 
      69L, 25L, 33L, 36L, 44L, 45L, 9L, 34L, 68L, 13L, 6L, 61L, 
      53L, 65L, 51L, 31L, 41L, 39L, 37L, 49L, 22L, 58L, 47L, 71L, 
      40L, 60L, 19L, 18L, 64L, 10L, 62L, 59L, 42L, 7L, 11L, 4L, 
      52L, 32L, 38L, 8L, 54L, 20L, 12L, 24L, 1L, 63L, 3L, 16L, 
      57L, 70L, 43L, 15L, 2L, 46L, 30L, 35L, 56L, 23L, 48L, 26L, 
      14L, 50L, 67L, 29L, 28L, 27L, 17L, 21L, 66L, 55L, 5L, 69L, 
      25L, 33L, 36L, 44L, 45L, 9L, 34L, 68L, 13L, 6L, 61L, 53L, 
      65L, 51L, 31L, 41L, 39L, 37L, 49L, 22L), .Label = c("Administrative Council of Economic Defense (CADE)                              ", 
      "Air Force Real Estate Funding Agency (CFIAE)                                   ", 
      "Alexandre Gusmao Foundation (FUNAG)                                            ", 
      "Amazon Development Superintendency (SUDAM)                                     ", 
      "Applied Economic Research Institute (IPEA)                                     ", 
      "Brazilian Agricultural Research Corporation (EMBRAPA)                          ", 
      "Brazilian Communication Company (EBC)                                          ", 
      "Brazilian Company of Urban Railway (CBTU)                                      ", 
      "Brazilian Institute of Environment and Renewable Natural Resources (IBAMA)     ", 
      "Brazilian Institute of Geography and Statistics (IBGE)                         ", 
      "Brazilian Institute of Museums (IBRAM)                                         ", 
      "Brazilian Military Material Industry (IMBEL)                                   ", 
      "Brazilian Securities Comission (CVM)                                           ", 
      "Brazilian Space Agency (AEB)                                                   ", 
      "Brazilian Tourism Company (EMBRATUR)                                           ", 
      "Brazilian Urban Railway (TRENSUBR)                                             ", 
      "Central Bank (BACEN)                                                           ", 
      "Chico Mendes Institute (ICMBio)                                                ", 
      "Civil Aviation National Agency (ANAC)                                          ", 
      "Cultural Foundation Palmares                                                   ", 
      "Dom Pedro II School                                                            ", 
      "Energy Research Company (EPE)                                                  ", 
      "Engineering, Construction and Railway (VALEC)                                  ", 
      "Excellence center in advanced electronic technology (CEITEC)                   ", 
      "Federal Centre of Educational Technology Celso Suckow da Fonseca (CEFET-RJ)    ", 
      "Graduate students improvement coordination (CAPES)                             ", 
      "Hospital Cristo Redentor S.A.                                                  ", 
      "Hospital F\x90mina S.A                                                            ", 
      "Hospital Nossa Senhora da Concei\x8d\x8bo S.A                                        ", 
      "Housing Building Fund for Mariners (CCCPMC)                                    ", 
      "Indigenous National Foundation (FUNAI)                                         ", 
      "Institute of the Historical and Artistic National Heritage (IPHAN)             ", 
      "Joaquim Nabuco Foundation                                                      ", 
      "Jorge Duprat Figueiredo Foundation (FUNDACENTRO)                               ", 
      "Manaus Free Trade Zone Superintendency (SUFRAMA)                               ", 
      "Minas Gerais Federal Centre of Educational Technology (CEFET-MG)               ", 
      "Mineral Resources Research Institute (CPRM)                                    ", 
      "National  Agency of Land Transport (ANTT)                                      ", 
      "National  Agency of Sanitary Supervision (ANVISA)                              ", 
      "National  Agency of Supplementary Health (ANS)                                 ", 
      "National  Agency of Water Transport (ANTAQ)                                    ", 
      "National Agency of Electrical Energy (ANEEL)                                   ", 
      "National Agency of Oil, Natural Gas and Biofuel (ANP)                          ", 
      "National Commission of Nuclear Energy (CNEN)                                   ", 
      "National Company of Food Supply (CONAB)                                        ", 
      "National Council of Scientific and Technological Development (CNPq)            ", 
      "National Department of Draught Prevention (DNOCS)                              ", 
      "National Department of Infrasctructure Transport (DNIT)                        ", 
      "National Department of Mineral Production (DNPM)                               ", 
      "National Development Trust (FND)                                               ", 
      "National Health Foundation (FUNASA)                                            ", 
      "National Institute of Colonization and Land Reform (INCRA)                     ", 
      "National Institute of Industrial Property (INPI)                               ", 
      "National Institute of Metrology, Normalization and Industrial Quality (Inmetro)", 
      "National Institute of Social Security (INSS)                                   ", 
      "National Institute of Studies and Educational Research  Anisio Teixeira (INEP) ", 
      "National Institute of Technology Information (ITI)                             ", 
      "National Library Foundation                                                    ", 
      "National Movies Agency (ANCINE)                                                ", 
      "National School of Public Administration Foundation (ENAP)                     ", 
      "National Trust of Education Development (FNDE)                                 ", 
      "National Water Agency (ANA)                                                    ", 
      "Northeast Development Superintendency (SUDENE)                                 ", 
      "Oswaldo Cruz Foundation (FIOCRUZ)                                              ", 
      "Ozorio Foundation                                                              ", 
      "Porto Alegre Clinic Hospital                                                   ", 
      "Private Insurance Superintendency (SUSEP)                                      ", 
      "Rio de Janeiro Botanical Gardens Research Institute                            ", 
      "Rui Barbosa House Foundation                                                   ", 
      "Sao Francisco and Parnaiba Valleys Development Company (CODEVASF)              ", 
      "Telecom National Agency (ANATEL)                                               "
      ), class = "factor")), .Names = c("year", "totalex", "agency.type", 
  "unit"), row.names = c(NA, 100L), class = "data.frame")
  </code></pre>