r - how to plot x and y based on several conditions? -
i have dataframe, constructed follows:
col1<-c(0.10, 0.21, 0.34, 0.39, 0.54, 0.67,0.89) col2<-c (0,100,500,1000,3000,5000,8000 ) col3<-c ("b", "a","a","c", "c","b", "c" ) mydata<-data.frame(col1,col2,col3) > mydata col1 col2 col3 # 1 0.10 0 b # 2 0.21 100 # 3 0.34 500 # 4 0.39 1000 c # 5 0.54 3000 c # 6 0.67 5000 b # 7 0.89 8000 c here code create plot between col2 , col1:
plot(mydata$col2,mydata$col1, main = "plot of data", xlab = "x", ylab= "y", pch =c(21,21,21)[mydata$col3], bg=c("blue","grey", "red")[mydata$col3], ) legend("topright",pch=c(21,21,21), title="categories:", c("a","b", "c"),pt.bg=c("blue","red","grey")) it creates plot:
i have problems in codes:
1, there should 7 points in plot, 1 has been covered topright box. there better method points display?
2, want have different scales in x-axis label tick marks desired interval, 
. see interval between 100 , 500 same 3000 , 8000, smaller values not suppressed extremely left side, want. how achieve that?
3, seems in syntax pch =c(21,21,21)[mydata$col3], bg=c("blue","grey", "red")[mydata$col3], haven't specified colour maps "a", "b" or "c". if want respectively map colours "blue","grey", "red" "a", "b" , "c" given in col3. how specify it?
any advice appreciated.
for second one, use customize axis. in case, want customize x axis. in plot function, need add xaxt="n", disable original x axis. use axis add yours. in case, try
axis(1, at=c(a,b,c,d,e),labels=c(a,b,c,d,e),xxx,xxx) where a, b,c,d,e values want have.
example:
y <- x <- c(1:5) plot(x, y,type="l", xaxt="n") axis(1, at=c(1,1.3,1.5,1.7,2.8),labels=c(1,1.3,1.5,1.7,2.8)) 
for third question, how adding column of mapping colors dataframe? following: instance,
mydata$color <-ifelse(mydata$col3=="a","blue",ifelse(mydata$col3=="b","red","grey")) which maps color blue, b color red , c grey. , in plot,
plot(mydata$col2,mydata$col1,xxxxxx, bg=mydata$color, ) 
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