I have used ggplot to create a graph on which the y-axis is on the log scale. (see data and code, below.) I would like to add minor tick marks, which will also be on the log scale. The data and code are below. I hope somone can tell me how I can modify the ggplot code so it produces minor tick marks on a log scale. Thank you, John PopByDayByAQIminus <- dget( structure(list(Day = c("25", "25", "25", "25", "25", "25", "25", "26", "26", "26", "26", "26", "26", "26", "27", "27", "27", "27", "27", "27", "27", "28", "28", "28", "28", "28", "28", "28"), AQI_Cat = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 1L, 2L, 3L, 4L, 5L, 6L, 7L), levels = c("Good", "Moderate", "Unhealthy For Some", "Unhealthy", "Very Unhealthy", "Hazardous1", "Hazardous2"), class = "factor"), TotalPop = c(3751359, 35043, 4285, 11581, 26241, 17456, 18406, 3654557, 153002, 29954, 8452, 7719, 10687, 10430, 3654344, 104843, 57277, 24910, 15165, 4680, 13582, 3116416, 516504, 149029, 29640, 33468, 10862, 18882)), class = "data.frame", row.names = c(NA, -28L)))
PopByDayByAQIminus ggplot(PopByDayByAQIminus,aes(x=AQI_Cat,y=TotalPop/1000000, group=Day,color=Day,shape=factor(Day),linetype = factor(Day)))+ labs(title=title,x="Air Quality Index") + geom_point(size=4,alpha=0.7)+ geom_line(linewidth=1.5,alpha=0.3)+ theme(axis.text.x=element_text(angle = -15, hjust = 0))+ scale_y_continuous(trans='log10') scale_y_continuous(breaks=seq(0,4000000,by=1000000)) John David Sorkin M.D., Ph.D. Professor of Medicine, University of Maryland School of Medicine; Associate Director for Biostatistics and Informatics, Baltimore VA Medical Center Geriatrics Research, Education, and Clinical Center; PI Biostatistics and Informatics Core, University of Maryland School of Medicine Claude D. Pepper Older Americans Independence Center; Senior Statistician University of Maryland Center for Vascular Research; Division of Gerontology and Paliative Care, 10 North Greene Street GRECC (BT/18/GR) Baltimore, MD 21201-1524 Cell phone 443-418-5382 ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide https://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.