💡 KEY LEARNINGS:
■ MDS - Multi-Dimension Scaling
§ a different method for dimension reduction
§ try to maintain the distance in low dimension space
■ Perception Map - a marketing tool that visualize …
§ The similarity among the brands
§ The correlation among the brand attributes
§ The relationship between the brands and the attributes
::p_load(dplyr, FactoMineR, factoextra) pacman
load("data/cafe.rdata")
row.names(cafe) = cafe[,1]
= cafe[,-1]
cafe cafe
種類樣式 產品風格 整體產品 公司形象 品牌印象 知名度 專業表現 可信度
丹堤 3.10 2.55 2.85 2.98 2.28 2.66 2.42 2.22
星巴克 2.35 2.68 2.84 3.21 2.07 3.27 2.62 2.22
八五度 3.23 2.69 2.79 2.77 2.73 2.65 2.13 1.99
壹咖啡 2.90 2.62 2.74 2.70 2.57 2.66 2.41 2.09
理想品牌 2.56 3.17 3.19 2.71 1.72 2.23 2.81 2.50
We don’t have much data. Just 8 attributes and 5 brands. Yet it is still challenging to compare all of the 8 attributes on this 5 brand at once.
dist()
cmdscale()
for MDS analysis.= dist(cafe, method = "euclidean")
d <- cmdscale(d, eig = TRUE, k = 2) fit
= rownames(cafe); percepts=colnames(cafe)
brands $x = fit$points[, 1]
cafe$y = fit$points[, 2]
cafeplot(cafe$x, cafe$y, pch = 19, xlim=c(-1.5,1.5), ylim=c(-1,1.5))
= c(3, 3, 4, 4, 3)
bpos text(cafe$x, cafe$y, pos=bpos, offset=0.5, labels = brands)
Perceived difference among the brands are represented as the corresponding distances on the map.
Furthermore, we can also plot the unit vectors for the original dimension on the map.
plot(cafe$x, cafe$y, pch = 19, xlim=c(-3.5,2), ylim=c(-2.2,2.5))
for(i in 1:length(percepts)) {
= lm(sprintf("%s ~ x + y",percepts[i]), data=cafe)
m = 1/m$coef[2]; d = 1/m$coef[3]
c = c*c + d*d
cd2 = (c * d * d)/cd2
px = (c * c * d)/cd2
py arrows(0,0,px,py,col="pink",length=0)
text(px, py, col="red", cex=0.75, labels = percepts[i])
}text(cafe$x, cafe$y, pos=bpos, offset=0.5, cex=0.75, labels = brands)
The result of MDS is quite similar to that of PCA
PCA(cafe[1:8], graph=F) %>% fviz_pca_biplot(
repel=T, col.var="blue", col.ind="red",
labelsize=3, pointshape=16, pointsize=3)
🗿 DISCUSSION 1:
■ What can you tell from the Perception Map?
■ Are these finding useful (for marketing)?
🗿 DISCUSSION 2:
■ Why do we do dimension reduction?
■ What is the common logic of dimension reduction algorithm?< br> ■ What are the pro and con’s of dimension reduction?
■ What are the 3 important information we can learn from dimension reduction?