What do hjust and vjust do when making a plot using ggplot

Question

Every time I make a plot using ggplot  I spend a little while trying different values for hjust and vjust in a line like     opts axis text x   theme text hjust   0 5     to get the axis labels to line up where the axis labels almost touch the axis  and are flush against it  justified to the axis  so to speak   However  I don t really understand what s going on  Often  hjust   0 5 gives such dramatically different results from hjust   0 6  for example  that I haven t been able to figure it out just by playing around with different values    Can anyone point me to a comprehensive explanation of how hjust and vjust options work

User · Accepted Answer

The value of hjust and vjust are only defined between 0 and 1    0 means left-justified 1 means right-justified   Source  ggplot2  Hadley Wickham  page 196   Yes  I know that in most cases you can use it beyond this range  but don t expect it to behave in any specific way   This is outside spec    hjust controls horizontal justification and vjust controls vertical justification   An example should make this clear   td  lt - expand grid      hjust c 0  0 5  1       vjust c 0  0 5  1       angle c 0  45  90       text  text     ggplot td  aes x hjust  y vjust          geom point         geom text aes label text  angle angle  hjust hjust  vjust vjust          facet grid  angle        scale x continuous breaks c 0  0 5  1   expand c 0  0 2         scale y continuous breaks c 0  0 5  1   expand c 0  0 2         To understand what happens when you change the hjust in axis text  you need to understand that the horizontal alignment for axis text is defined in relation not to the x-axis  but to the entire plot  where this includes the y-axis text     This is  in my view  unfortunate   It would be much more useful to have the alignment relative to the axis    DF  lt - data frame x LETTERS 1 3  y 1 3  p  lt - ggplot DF  aes x y     geom point          ylab  Very long label for y         theme axis title y element text angle 0     p1  lt - p   theme axis title x element text hjust 0     xlab  X-axis at hjust 0   p2  lt - p   theme axis title x element text hjust 0 5     xlab  X-axis at hjust 0 5   p3  lt - p   theme axis title x element text hjust 1     xlab  X-axis at hjust 1    library ggExtra  align plots p1  p2  p3        To explore what happens with vjust aligment of axis labels   DF  lt - data frame x c  a na   b   cdefghijk   l   y 1 4  p  lt - ggplot DF  aes x y     geom point    p1  lt - p   theme axis text x element text vjust 0  colour  red               xlab  X-axis labels aligned with vjust 0   p2  lt - p   theme axis text x element text vjust 0 5  colour  red               xlab  X-axis labels aligned with vjust 0 5   p3  lt - p   theme axis text x element text vjust 1  colour  red               xlab  X-axis labels aligned with vjust 1     library ggExtra  align plots p1  p2  p3

User · Answer

Probably the most definitive is Figure B 1 d  of the ggplot2 book  the appendices of which are available at http   ggplot2 org book appendices pdf     However  it is not quite that simple   hjust and vjust as described there are how it works in geom text and theme text  sometimes    One way to think of it is to think of a box around the text  and where the reference point is in relation to that box  in units relative to the size of the box  and thus different for texts of different size    An hjust of 0 5 and a vjust of 0 5 center the box on the reference point   Reducing hjust moves the box right by an amount of the box width times 0 5-hjust   Thus when hjust 0  the left edge of the box is at the reference point   Increasing hjust moves the box left by an amount of the box width times hjust-0 5   When hjust 1  the box is moved half a box width left from centered  which puts the right edge on the reference point   If hjust 2  the right edge of the box is a box width left of the reference point  center is 2-0 5 1 5 box widths left of the reference point   For vertical  less is up and more is down   This is effectively what that Figure B 1 d  says  but it extrapolates beyond  0 1    But  sometimes this doesn t work   For example  DF  lt - data frame x c  a   b   cdefghijk   l   y 1 4  p  lt - ggplot DF  aes x y     geom point    p   opts axis text x theme text vjust 0   p   opts axis text x theme text vjust 1   p   opts axis text x theme text vjust 2     The three latter plots are identical   I don t know why that is   Also  if text is rotated  then it is more complicated   Consider  p   opts axis text x theme text hjust 0  angle 90   p   opts axis text x theme text hjust 0 5 angle 90   p   opts axis text x theme text hjust 1  angle 90   p   opts axis text x theme text hjust 2  angle 90     The first has the labels left justified  against the bottom   the second has them centered in some box so their centers line up  and the third has them right justified  so their right sides line up next to the axis    The last one  well  I can t explain in a coherent way   It has something to do with the size of the text  the size of the widest text  and I m not sure what else

[r] What do hjust and vjust do when making a plot using ggplot?

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