ggplot2 line chart gives geom path Each group consist of only one observation Do you need to adjust the group aesthetic

Question

With this data frame   df     year pollution 1 1999 346 82000 2 2002 134 30882 3 2005 130 43038 4 2008  88 27546   I try to create a line chart like this     plot5  lt - ggplot df  aes year  pollution                geom point                geom line                labs x    Year   y    Particulate matter emissions  tons    title    Motor vehicle emissions in Baltimore     The error I get is      geom path  Each group consist of only one observation  Do you need to   adjust the group aesthetic    The chart appears as a scatter plot even though I want a line chart  I tried to replace geom line   with geom line aes group   year   but that didn t work    In an answer I was told to convert year to a factor variable  I did and the problem persists  This is the output of str df  and dput df     data frame     4 obs  of  2 variables     year       num  1 2 3 4    pollution  num  1 4 1d   346 8 134 3 130 4 88 3     - attr     dimnames   List of 1            chr   1999   2002   2005   2008   structure list year   c 1  2  3  4   pollution   structure c 346 82   134 308821199349  130 430379885892  88 275457392443    Dim   4L   Dimnames   list      c  1999    2002    2005    2008        Names   c  year     pollution    row names   c NA  -4L   class    data frame

User · Answer

I had similar problem with the data frame:

group time weight.loss
1 Control  wl1    4.500000
2    Diet  wl1    5.333333
3  DietEx  wl1    6.200000
4 Control  wl2    3.333333
5    Diet  wl2    3.916667
6  DietEx  wl2    6.100000
7 Control  wl3    2.083333
8    Diet  wl3    2.250000
9  DietEx  wl3    2.200000

I think the variable for x axis should be numeric, so that geom_line knows how to connect the points to draw the line.

after I change the 2nd column to numeric:

 group time weight.loss
1 Control    1    4.500000
2    Diet    1    5.333333
3  DietEx    1    6.200000
4 Control    2    3.333333
5    Diet    2    3.916667
6  DietEx    2    6.100000
7 Control    3    2.083333
8    Diet    3    2.250000
9  DietEx    3    2.200000

then it works.

User · Answer

I got a similar prompt  It was because I had specified the x-axis in terms of some percentage  for example  10 A  20 B        So an alternate approach could be that you multiply these values and write them in the simplest form

User · Answer

Start up R in a fresh session and paste this in   library ggplot2   df  lt - structure list year   c 1  2  3  4   pollution   structure c 346 82   134 308821199349  130 430379885892  88 275457392443    Dim   4L   Dimnames   list      c  1999    2002    2005    2008        Names   c  year     pollution    row names   c NA  -4L   class    data frame    df    lt - lapply df  as numeric    make all columns numeric  ggplot df  aes year  pollution                geom point                geom line                labs x    Year                    y    Particulate matter emissions  tons                     title    Motor vehicle emissions in Baltimore

User · Answer

I found this can also occur if the most of the data plotted is outside of the axis limits  In that case  adjust the axis scales accordingly

User · Answer

You only have to add group   1 into the ggplot or geom line aes        For line graphs  the data points must be grouped so that it knows which points to connect  In this case  it is simple -- all points should be connected  so group 1  When more variables are used and multiple lines are drawn  the grouping for lines is usually done by variable    Reference  Cookbook for R  Chapter  Graphs Bar and line graphs  ggplot2   Line graphs   Try this   plot5  lt - ggplot df  aes year  pollution  group   1              geom point              geom line              labs x    Year   y    Particulate matter emissions  tons                   title    Motor vehicle emissions in Baltimore

User · Answer

You get this error because one of your variables is actually a factor variable   Execute  str df     to check this  Then do this double variable change to keep the year numbers instead of transforming into  1 2 3 4  level numbers   df year  lt - as numeric as character df year     EDIT  it appears that your data frame has a variable of class  array  which might cause the pb  Try then   df  lt - data frame apply df  2  unclass     and plot again

[r] ggplot2 line chart gives "geom_path: Each group consist of only one observation. Do you need to adjust the group aesthetic?"

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