# Function to calculate cosine dissimilarity matrix
# Thanks to: https://stats.stackexchange.com/a/149865/121489
cos.sim <- function(ma, mb) {
    mat <- tcrossprod(ma, mb);
    t1 <- sqrt(apply(ma, 1, crossprod));
    t2 <- sqrt(apply(mb, 1, crossprod));
    return(mat / outer(t1, t2));
}

# Generate sample data
set.seed(2017);
x1 <- matrix(rnorm(45), ncol = 5);

# Calculate the cosine dissimilarity matrix
m <- cos.sim(x1, x1);

# Show heatmap
library(tidyverse);
m %>%
    as_tibble() %>%
    rownames_to_column("x1") %>%
    gather(x2, value, 2:10) %>%
    mutate(x2 = gsub("V", "", x2)) %>%
    ggplot(aes(x1, x2)) + geom_tile(aes(fill = value));