ck_coherence_matrix <- function(coherence_data) {
  
  colnames(coherence_data) <- coherence_columns
  rownames(coherence_data) <- coherence_columns
  
  melt_coherence_data = melt(as.matrix(coherence_data))
  
  coherence_data_plot <- ggplot(data = melt_coherence_data, 
                                aes(x=Var1, y=Var2, fill=value)
  ) + 
    geom_tile(color = "white")  
  
  coherence_data_plot <- coherence_data_plot + theme_minimal() 
  
  coherence_data_plot <- coherence_data_plot + scale_fill_gradient2(low="white", high="red", 
                                                                    midpoint=0.5, limit=c(0.0,1.0), space = "Lab", 
                                                                    name = "Coherence", 
                                                                    guide = "colorbar", 
                                                                    breaks = c(0.2, 0.4, 0.6)
  )
  
  coherence_data_plot <- coherence_data_plot + 
    scale_x_discrete(name="", position = "top") + 
    scale_y_discrete(name="",
                     limits = rev(levels(melt_coherence_data$Var2))
    )
  
  coherence_data_plot <- coherence_data_plot + 
    theme(legend.title = element_text(size = 10, face = "bold"), 
          legend.text = element_text(size=8, face = "bold"), 
          legend.background=element_rect(fill = "gray90", size = 0.5))
  
  coherence_data_plot <- coherence_data_plot + 
    theme(axis.text.x = element_text(angle=45, vjust=0, size=12, hjust=0, face="bold"), 
          axis.title.x = element_text(size = 16, face="bold"), 
          axis.title.y = element_text(size = 16, face="bold"), 
          axis.text.y = element_text(size = 12, face = "bold")
    )
  
  coherence_data_plot <- coherence_data_plot + 
    theme(panel.border = element_rect(fill=NA, size=1))
  
  coherence_data_plot <-	coherence_data_plot + coord_fixed()
  
  return(coherence_data_plot)
}