The solutions given below are just one way of obtaining the desired plots! There are probably several different ways you could code to get the same plots.

1 ggplot2 part-I

1.1 Exercise I

All you need to do is to replace the filename raw_counts.txt with each of the different files to look at the differences between different normalization methods.

1.2 Exercise II

Task   Plot 1:

gc_raw <- read.table(file = "data/counts_raw.txt", sep = "\t", header = T)
gc_filt <- read.table(file = "data/counts_filtered.txt", sep = "\t", header = T)
gc_vst <- read.table(file = "data/counts_vst.txt", sep = "\t", header = T)
gc_deseq <- read.table(file = "data/counts_deseq2.txt", sep = "\t", header = T)
md <- read.table("data/metadata.csv", header = T, sep = ";")

gene_counts_all <- 
  gc_raw %>% gather(Sample_ID, Raw, -Gene) %>%
  full_join(gc_filt %>% gather(Sample_ID, Filtered, -Gene), by = c("Gene", "Sample_ID")) %>%
  full_join(gc_vst %>% gather(Sample_ID, VST, -Gene), by = c("Gene", "Sample_ID")) %>%
  full_join(gc_deseq %>% gather(Sample_ID, DESeq2, -Gene), by = c("Gene", "Sample_ID")) %>%
  gather(Method, count, Raw:DESeq2) %>%
  filter(!is.na(count)) %>%
  full_join(md, by = "Sample_ID")

gene_counts_all$Time <- factor(gene_counts_all$Time, levels = c("t0","t2","t6","t24"))
gene_counts_all$Replicate <- factor(gene_counts_all$Replicate, levels = c("A","B","C"))
gene_counts_all$Method <- factor(gene_counts_all$Method, levels = c("Raw","Filtered","DESeq2","VST"))

gene_counts_all %>% 
  group_by(Time, Replicate, Method) %>% 
  summarise(mean=mean(log10(count +1)),se=se(log10(count +1))) %>%
  ggplot(aes(x= Time, y= mean, fill = Replicate)) + 
  geom_bar(position = position_dodge2(), stat = "identity") +
  geom_errorbar(aes(ymin=mean-se, ymax=mean+se), position = position_dodge2(.9, padding = .6)) +
  facet_wrap(~Method, scales = "free")

Task   Plot 2:

gene_counts_all %>% 
  group_by(Time, Replicate, Method) %>% 
  ggplot() +
  geom_boxplot(mapping = aes(x = Sample_Name, y = log10(count + 1), fill = Time)) +
  facet_wrap(~Method*Replicate, ncol = 3, scales = "free")

2 ggplot2 part-II

2.1 Exercise I

gc_long %>% 
  group_by(Time, Replicate) %>% 
  summarise(mean=mean(log10(count +1)),se=se(log10(count +1))) %>%
  ggplot(aes(x=Time, y=mean, color = Replicate)) +
  facet_wrap(~Replicate) +
  geom_line(aes(group=1), stat= "identity", size = 2) +
  scale_x_discrete(limits= c("t0", "t2", "t24")) +
  scale_y_continuous(limits = c(0.4,0.8), breaks = seq(0.4,0.8,0.05)) +
  guides(color="none") +
  ylab(label = "mean(log10(count + 1))") +
  theme_light() +
  theme(axis.text = element_text(face="bold", size=12),
        axis.title = element_text(face="bold", color = "#C84DF9", size=14),
        axis.ticks = element_blank())

2.2 Exercise II

p4 <- ggplot(data=iris,mapping=aes(x=Sepal.Length, y = Sepal.Width, color = Species)) +
  geom_point(size = 3, alpha = 0.6) +
  theme_classic(base_size = 12) +
  border() 

d1 <- ggplot(data=iris,mapping=aes(Sepal.Length, fill = Species)) +
  geom_density(alpha = 0.6) +
  theme_classic() +
  clean_theme() +
  theme(legend.position = "none")

d2 <- ggplot(data=iris,mapping=aes(Sepal.Width, fill = Species)) +
  geom_density(alpha = 0.6) +
  theme_classic() +
  clean_theme() +
  theme(legend.position = "none") +
  rotate()

ggarrange(d1, NULL, p4, d2, 
          ncol = 2, nrow = 2,  align = "hv", 
          widths = c(3, 1), heights = c(1, 3),
          common.legend = TRUE)

2.3 Exercise III

Eigenvalues <- gc_mds$eig
Variance <- Eigenvalues / sum(Eigenvalues) 
Variance1 <- 100 * signif(Variance[1], 3)
Variance2 <- 100 * signif(Variance[2], 3)

gc_mds_long <- gc_mds$points %>%
  as.data.frame() %>%
  rownames_to_column("Sample_ID") %>%
  full_join(md, by = "Sample_ID")

gc_mds_long$Sample_Name <- factor(gc_mds_long$Sample_Name, levels = c("t0_A","t0_B","t0_C","t2_A","t2_B","t2_C","t6_A","t6_B","t6_C","t24_A","t24_B","t24_C"))
gc_mds_long$Time <- factor(gc_mds_long$Time, levels = c("t0","t2","t6","t24"))
gc_mds_long$Replicate <- factor(gc_mds_long$Replicate, levels = c("A","B","C"))

ggplot(gc_mds_long, aes(x=V1, y=V2, color = Time)) +
  geom_point(size = 3, aes(shape = Replicate)) +
  xlab(paste("PCO1: ", Variance1, "%")) +
  ylab(paste("PCO2: ", Variance2, "%")) +
  geom_vline(xintercept = 0, linetype=2) +
  geom_hline(yintercept = 0, linetype=2) +
  theme_bw() +
  theme(panel.grid.major = element_blank(), 
        panel.grid.minor = element_blank()) 

3 Session info

sessionInfo()
## R version 4.1.3 (2022-03-10)
## Platform: x86_64-pc-linux-gnu (64-bit)
## Running under: Ubuntu 18.04.6 LTS
## 
## Matrix products: default
## BLAS:   /usr/lib/x86_64-linux-gnu/openblas/libblas.so.3
## LAPACK: /usr/lib/x86_64-linux-gnu/libopenblasp-r0.2.20.so
## 
## locale:
##  [1] LC_CTYPE=C.UTF-8       LC_NUMERIC=C           LC_TIME=C.UTF-8       
##  [4] LC_COLLATE=C.UTF-8     LC_MONETARY=C.UTF-8    LC_MESSAGES=C.UTF-8   
##  [7] LC_PAPER=C.UTF-8       LC_NAME=C              LC_ADDRESS=C          
## [10] LC_TELEPHONE=C         LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C   
## 
## attached base packages:
## [1] grid      stats     graphics  grDevices utils     datasets  methods  
## [8] base     
## 
## other attached packages:
##  [1] shiny_1.7.2            ggrepel_0.9.1          wesanderson_0.3.6     
##  [4] gridExtra_2.3          jpeg_0.1-9             ggpubr_0.4.0          
##  [7] cowplot_1.1.1          ggthemes_4.2.4         scales_1.2.1          
## [10] forcats_0.5.2          stringr_1.4.1          purrr_0.3.5           
## [13] readr_2.1.3            tidyr_1.2.1            tibble_3.1.8          
## [16] tidyverse_1.3.2        reshape2_1.4.4         ggplot2_3.3.6         
## [19] formattable_0.2.1      kableExtra_1.3.4       dplyr_1.0.10          
## [22] lubridate_1.8.0        leaflet_2.1.1          yaml_2.3.5            
## [25] fontawesome_0.3.0.9000 captioner_2.2.3        bookdown_0.29         
## [28] knitr_1.40            
## 
## loaded via a namespace (and not attached):
##  [1] nlme_3.1-155        fs_1.5.2            webshot_0.5.4      
##  [4] httr_1.4.4          tools_4.1.3         backports_1.4.1    
##  [7] bslib_0.4.0         utf8_1.2.2          R6_2.5.1           
## [10] DBI_1.1.3           mgcv_1.8-39         colorspace_2.0-3   
## [13] withr_2.5.0         processx_3.7.0      tidyselect_1.2.0   
## [16] compiler_4.1.3      cli_3.4.1           rvest_1.0.3        
## [19] xml2_1.3.3          labeling_0.4.2      sass_0.4.2         
## [22] callr_3.7.2         systemfonts_1.0.4   digest_0.6.29      
## [25] rmarkdown_2.17      svglite_2.1.0       pkgconfig_2.0.3    
## [28] htmltools_0.5.3     dbplyr_2.2.1        fastmap_1.1.0      
## [31] highr_0.9           htmlwidgets_1.5.4   rlang_1.0.6        
## [34] readxl_1.4.1        xaringan_0.26       rstudioapi_0.14    
## [37] jquerylib_0.1.4     generics_0.1.3      farver_2.1.1       
## [40] jsonlite_1.8.2      crosstalk_1.2.0     car_3.1-0          
## [43] googlesheets4_1.0.1 magrittr_2.0.3      Matrix_1.5-1       
## [46] Rcpp_1.0.9          munsell_0.5.0       fansi_1.0.3        
## [49] abind_1.4-5         lifecycle_1.0.3     stringi_1.7.8      
## [52] carData_3.0-5       plyr_1.8.7          promises_1.2.0.1   
## [55] crayon_1.5.2        lattice_0.20-45     haven_2.5.1        
## [58] splines_4.1.3       hms_1.1.2           ps_1.7.1           
## [61] pillar_1.8.1        ggsignif_0.6.3      reprex_2.0.2       
## [64] glue_1.6.2          evaluate_0.17       modelr_0.1.9       
## [67] httpuv_1.6.6        vctrs_0.4.2         tzdb_0.3.0         
## [70] cellranger_1.1.0    gtable_0.3.1        assertthat_0.2.1   
## [73] cachem_1.0.6        xfun_0.33           mime_0.12          
## [76] xtable_1.8-4        broom_1.0.1         later_1.3.0        
## [79] rstatix_0.7.0       googledrive_2.0.0   viridisLite_0.4.1  
## [82] gargle_1.2.1        memoise_2.0.1       ellipsis_0.3.2