Plotting multiple curves same graph and same scale

Question

This is a follow-up of this question   I wanted to plot multiple curves on the same graph but so that my new curves respect the same y-axis scale generated by the first curve   Notice the following example   y1  lt - c 100  200  300  400  500  y2  lt - c 1  2  3  4  5  x  lt - c 1  2  3  4  5     first plot plot x  y1     second plot par new   TRUE  plot x  y2  axes   FALSE  xlab       ylab         That actually plots both sets of values on the same coordinates of the graph  because I m hiding the new y-axis that would be created with the second plot    My question then is how to maintain the same y-axis scale when plotting the second graph

User · Answer

I m not sure what you want  but i ll use lattice   x   rep x 2  y   c y1 y2  fac data   as factor rep 1 2 each 5   df   data frame x x y y z fac data    this create a data frame where I have a factor variable  z  that tells me which data I have  y1 or y2    Then  just plot  xyplot y  x z  df    or maybe xyplot x  y z  df

User · Answer

The typical method would be to use plot just once to set up the limits  possibly to include the range of all series combined  and then to use points and lines to add the separate series   To use plot multiple times with par new TRUE   you need to make sure that your first plot has a proper ylim to accept the all series  and in another situation  you may need to also use the same strategy for xlim      first plot plot x  y1  ylim range c y1 y2       second plot  EDIT  needs to have same ylim par new   TRUE  plot x  y2  ylim range c y1 y2    axes   FALSE  xlab       ylab           This next code will do the task more compactly  by default you get numbers as points but the second one gives you typical R-type- points      matplot x  cbind y1 y2     matplot x  cbind y1 y2   pch 1

User · Answer

My solution is to use ggplot2  It takes care of these types of things automatically  The biggest thing is to arrange the data appropriately   y1  lt - c 100  200  300  400  500  y2  lt - c 1  2  3  4  5  x  lt - c 1  2  3  4  5  df  lt - data frame x rep x 2   y c y1  y2   class c rep  y1   5   rep  y2   5      Then use ggplot2 to plot it  library ggplot2  ggplot df  aes x x  y y  color class     geom point     This is saying plot the data in df  and separate the points by class   The plot generated is

User · Answer

points or lines comes handy if    y2 is generated later  or the new data does not have the same x but still should go into the same coordinate system    As your ys share the same x  you can also use matplot   matplot  x  cbind  y1  y2   pch   19       without the pch matplopt will plot the column numbers of the y matrix instead of dots

User · Answer

You aren t being very clear about what you want here  since I think  DWin s is technically correct  given your example code  I think what you really want is this   y1  lt - c 100  200  300  400  500  y2  lt - c 1  2  3  4  5  x  lt - c 1  2  3  4  5     first plot plot x  y1 ylim   range c y1 y2       Add points points x  y2    DWin s solution was operating under the implicit assumption  based on your example code  that you wanted to plot the second set of points overlayed on the original scale  That s why his image looks like the points are plotted at 1  101  etc  Calling plot a second time isn t what you want  you want to add to the plot using points  So the above code on my machine produces this     But DWin s main point about using ylim is correct

[r] Plotting multiple curves same graph and same scale

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