r - Can't add points to a plot: Error: A continuous variable can not be mapped to shape -

i'm trying add points generated plot

dataframe used in original plot looks this:

> head(df)     fa   va   ca   rs    ch fsd tsd       d    p    s    cluster q 1  7.4 0.29 0.50  1.8 0.042  35 127 0.99370 3.45 0.50 10.2       1 7 2 10.0 0.41 0.45  6.2 0.071   6  14 0.99702 3.21 0.49 11.8       2 7 3  7.8 0.26 0.27  1.9 0.051  52 195 0.99280 3.23 0.50 10.9       3 6 4  6.9 0.32 0.30  1.8 0.036  28 117 0.99269 3.24 0.48 11.0       1 6 5  6.8 0.37 0.28  1.9 0.024  64 106 0.98993 3.45 0.60 12.6       1 8 6  6.2 0.25 0.44 15.8 0.057  39 167 0.99804 3.14 0.51  9.2       3 5 

i generate plot this:

> ggplot(data=df, aes(x=p, y=tsd, color=cluster )) +  +     geom_point() +  +     geom_point(data=centers, aes(x=p,y=tsd, color='center')) + +     geom_point(data=centers, aes(x=p,y=tsd, color='center'), size=52, alpha=.3, show_guide=false) 

now need add more points plot. dataframe want add looks this:

> head(df2)     fa   va   ca   rs    ch fsd tsd       d    p    s    cluster q 1  6.2 0.23 0.35  0.7 0.051  24 111 0.99160 3.37 0.43 11.0       1 3 2 11.8 0.23 0.38 11.1 0.034  15 123 0.99970 2.93 0.55  9.7       1 3 3  6.6 0.36 0.29  1.6 0.021  24  85 0.98965 3.41 0.61 12.4       1 9 4  9.1 0.27 0.45 10.6 0.035  28 124 0.99700 3.20 0.46 10.4       1 9 5  8.3 0.33 0.42  1.2 0.033  18  96 0.99110 3.20 0.32 12.4       1 3 6  7.4 0.24 0.36  2.0 0.031  27 139 0.99055 3.28 0.48 12.5       1 9 

this error

> last_plot() +  geom_point(data=df2, aes(x=tsd, y=p, shape=5, alpha=.7, size=4.5) , show_guide=false) error: continuous variable can not mapped shape