Assignment 11 - Recommender Systems

Overview

Sweetwater.com is a site that caters to musicians, producers, performers, and studio engineers, offering a huge catalogue of music-related products for both production and performance. My approach to this assignment was as follows:

  1. Perform a scenario design analysis.
  2. Discern how the recommender system works as best as can be done. For this step, I did the following:
    1. Collect a list of products recommended to me as an existing customer with a significant order history.
    2. Create a new account and collect a list of products recommended to a new customer with no order history.
    3. Categorize each product as one of the following, based on its primary use: guitar, drum, keyboard, studio.
    4. Compare my order history with the recommended products from each list and see how each one fared.
  3. Suggest improvements based on the above findings.

Scenario Design Analysis

  1. The target audience for the site is (obviously) the aforementioned individuals: musicians, producers, performers, and studio engineers. It carries equipment for primarily guitar-based music (guitar, bass, drums, keyboards, vocals), rather than woodwinds, brass, or orchestra equipment.
  2. The key goal of these people is usually to drink heavily. So maybe they should think about selling beer along with their effects pedals. A second key goal is to look and sound cool, which requires expensive equipment. This is where Sweetwater comes in: They do the “expensive” part of that very well. Well, in all fairness, they do have good deals and are normally right around where Amazon is. And their customer service is excellent. I’m on a first-name basis with my rep.
  3. Sweetwater helps their customers accomplish their dreams of rockstardom by making all of their gear sound like it will do everything you ever wanted without requiring any musical talent to actually use it. That’s not entirely accurate, but some of the product descriptions have that bent. The truth is, musicians love music gear, so it honestly isn’t too hard to sell us anything. I’ll bet a first-grader could write the product descriptions and they’d still sell as well. For example, “I LIK THISS GITRE IT IS KOOL U SHOOD BY IT FOR 1 MILION DOLLERS.” I mean, who could resist that kind of persuasion?

Sweetwater’s Recommendations

Sweetwater’s page includes three tabs of recommended products:

  • New arrivals image1

  • Top deals image2

  • What’s hot image3

Data Collection

This code reads in some text files that I scraped from my purchase history and from the sweetwater.com web site, both for my own account (with an order history) and for a fresh account I just created.

# Read tsv of purchases
purch <- read.delim("sweetwater_purchases.txt", header = F)
purch <- purch %>% rename(item = V1, category = V5) %>%
  select(item, category)

# Create data frame for customer recommendations
recommend <- data.frame(matrix(vector(), 0, 4), stringsAsFactors=F)

# Read tsv's of existing customer recommended items.
# Items will be in six files:
# 1. Existing customer - new arrivals
# 2. Existing customer - top deals
# 3. Existing customer - what's hot
# 4. New customer - new arrivals
# 5. New customer - top deals
# 6. New customer - what's hot
recommend <- read.delim("sweetwater_existing_newarr.txt", header = F)
recommend <- recommend %>%
  rename(item = V1, category = V2) %>%
  mutate(page = "new arrivals", customer = "existing")
tmp <- read.delim("sweetwater_existing_deals.txt", header = F)
tmp <- tmp %>%
  rename(item = V1, category = V2) %>%
  mutate(page = "top deals", customer = "existing")
recommend <- bind_rows(recommend, tmp)
tmp <- read.delim("sweetwater_existing_hot.txt", header = F)
tmp <- tmp %>%
  rename(item = V1, category = V2) %>%
  mutate(page = "what's hot", customer = "existing")
recommend <- bind_rows(recommend, tmp)
tmp <- read.delim("sweetwater_new_newarr.txt", header = F)
tmp <- tmp %>%
  rename(item = V1, category = V2) %>%
  mutate(page = "new arrivals", customer = "new")
recommend <- bind_rows(recommend, tmp)
tmp <- read.delim("sweetwater_new_deals.txt", header = F)
tmp <- tmp %>%
  rename(item = V1, category = V2) %>%
  mutate(page = "top deals", customer = "new")
recommend <- bind_rows(recommend, tmp)
tmp <- read.delim("sweetwater_new_hot.txt", header = F)
tmp <- tmp %>%
  rename(item = V1, category = V2) %>%
  mutate(page = "what's hot", customer = "new")
recommend <- bind_rows(recommend, tmp)
recommend <- recommend %>%
  arrange(customer, page, category, item)

# Display tables
kable(purch, caption = 
  "<i><font color=#000000><b>Table 1.</b> Purchase history.</font></i>") %>% 
  kable_styling(latex_options = "striped")
Table 1. Purchase history.
item category
sonuus G2M V3 Universal Guitar-to-MIDI Converter guitar
AKG D112 MKII Dynamic Bass Drum Microphone with Integrated Mount drum
Rode M5 Matched Pair Compact Condenser Microphones studio
Shure SM81 Small-diaphragm Condenser Microphone studio
Shure SM58S Cardioid Dynamic Vocal Microphone with On/Off Switch studio
Shure Beta 56A Supercardioid Dynamic Snare / Tom Microphone drum
Behringer U-Phoria UMC204HD USB Audio Interface studio
Pro Co EG-20 Excellines Instrument Cable - 20’ Straight-Straight studio
Remo Emperor Black Suede Drumhead - 14 1 $16.99 $16.99 drum Remo Emperor Black Suede Drumhead - 12 drum
Remo Emperor Black Suede Drumhead - 13 1 $23.99 $23.99 drum Remo Emperor Black Suede Drumhead - 16 drum
Gibson Accessories Les Paul Studio Pickguard - Black guitar
Audio-Technica ATH-M20x Closed-back Monitoring Headphones studio
Pro Co BP-20 Excellines Balanced Patch Cable - 20’ studio
Hosa YPP-136 Stereo Breakout 1/4 TRSF to Dual 1/4 TS - 6 studio
Vic Firth American Classic Drumsticks With Vic Grip - 5A - Wood Tip drum
Behringer U-Phoria UMC22 USB Audio Interface studio
Shure SM57 Cardioid Dynamic Instrument Microphone studio
D’Addario Planet Waves PW-CMIC-10 Classic Series Microphone Cable - 10’ studio
On-Stage Stands MS7701B Tripod Microphone Stand - Black studio
Pro Co EGSS-15 Excellines Instrument Cable - 15’ studio
D’Addario EJ11 Light 80/20 Bronze Acoustic Strings - .012-.053 guitar
D’Addario PW-P047E 1/4 Male Stereo to 1/8 Female Stereo Adapter studio
On-Stage Stands KSA7500 Universal 2nd Tier studio
Dunlop Egg Shaker - (2-pack) drum
Pro Co EXM-30 Excellines Microphone Cable - 30’ studio
On-Stage Stands MS7701B Euro Boom Microphone Stand - Black studio
PDP 800 Series Boom Cymbal Stand drum
MOTU MIDI Express XT 8x8 USB MIDI Interface keyboard
Roland RMIDI-B5-DUAL Black Series Dual MIDI Cable - 5’ keyboard
Pigtronix Infinity Looper Pedal guitar
Remo Pinstripe Ebony Bass Drumhead - 22 inch drum
Remo Ambassador Ebony Bass Drumhead - 22 inch drum 
kable(recommend, caption = 
  "<i><font color=#000000><b>Table 1.</b> Recommended products.</font></i>") %>% 
  kable_styling(latex_options = "striped")
Table 1. Recommended products.
item category page customer
Boss BCB-90X Deluxe Pedalboard and Case guitar new arrivals existing
Catalinbread Sabbra Cadabra Clearwell Edition Overdrive Pedal - Sweetwater Exclusive guitar new arrivals existing
D’Angelico Excel SS Semi-hollowbody Electric Guitar - Black Dog with Shield Tremolo guitar new arrivals existing
Dunlop DVP5 Volume (X) 8 Pedal guitar new arrivals existing
Electro-Harmonix Ripped Speaker Fuzz Pedal guitar new arrivals existing
Eventide MicroPitch Delay Pedal guitar new arrivals existing
Eventide UltraTap Multi-Tap Effects Pedal guitar new arrivals existing
Gibson Custom 60th Anniversary 1961 SG Les Paul Standard VOS Electric Guitar - Cherry Red guitar new arrivals existing
Gretsch G6136T Limited-edition Falcon Hollowbody Electric Guitar - Two Tone Copper/Sahara Metallic guitar new arrivals existing
Hercules Stands GS414B Plus Single Guitar Stand with Auto Grip System and Free HA700 Strap/Headphone Hook guitar new arrivals existing
Line 6 HX Stomp XL Guitar Multi-effects Floor Processor guitar new arrivals existing
Line 6 POD Go Wireless Guitar Multi-effects Floor Processor guitar new arrivals existing
PRS Limited Edition SE Parlor P20E Acoustic-electric Guitar - Antique White guitar new arrivals existing
PRS SE Standard 24 - Tobacco Sunburst guitar new arrivals existing
Strymon Flint Limited Edition Tremolo and Reverb - Black Knobs guitar new arrivals existing
Universal Audio UAFX Astra Modulation Machine Pedal guitar new arrivals existing
Boveda BVMFK-LG 2-way Humidity Control Kit - Large 3-pack guitar top deals existing
D’Addario EXP11 Light Coated 80/20 Bronze Acoustic Strings - .012-.053 4-pack guitar top deals existing
D’Addario EXP16 - Coated Phosphor Bronze Light Acoustic Strings 4-pack guitar top deals existing
D’Addario Humidipak Standard Replacement 9-pack guitar top deals existing
Dunlop 926 Lap Dawg Tonebar Guitar Slide guitar top deals existing
Dunlop NC65 Maintenance Station Neck Cradle guitar top deals existing
Ernie Ball Expression Series Overdrive Pedal guitar top deals existing
Korg Pitchblack Advance Tuner Pedal - Metallic Blue guitar top deals existing
Martin Authentic Acoustic Superior Performance Guitar Strings - 92/8 Phosphor Bronze Medium 3-pack guitar top deals existing
On-Stage Stands Standard Guitar Stand, Cable and Clip-On Tuner Pack guitar top deals existing
Pedaltrain Compact Gigging Pedalboard Kit with Truetone Power & EBS Premium Cables guitar top deals existing
Pedaltrain Performance Pedalboard Kit with Truetone Power & EBS Premium cables guitar top deals existing
Snark Silver Snark Clip-on Chromatic Tuner 3-pack guitar top deals existing
String Swing CC01K Guitar Keeper Wall Mount Guitar Hanger 2-pack - Black Walnut guitar top deals existing
TC Electronic Flashback 2 Mini Delay Pedal guitar top deals existing
Two Notes Torpedo C.A.B. M+ Speaker Simulator Pedal guitar top deals existing
Boss DS-1 Distortion Pedal guitar what’s hot existing
Boss Katana-50 MkII 1x12 inch 50-watt Combo Amp guitar what’s hot existing
Boss RC-1 Loop Station Looper Pedal guitar what’s hot existing
Boss RC-5 Loop Station Compact Phrase Recorder Pedal guitar what’s hot existing
Boss SD-1 Super Overdrive Pedal guitar what’s hot existing
Dunlop GCB95 Cry Baby Standard Wah Pedal guitar what’s hot existing
Fender Mustang LT 25 1x8 25-watt Combo Amp guitar what’s hot existing
Fishman Loudbox Mini BT 60-watt 1x6.5 Acoustic Combo Amp guitar what’s hot existing
Keeley Compressor Plus 4-Knob Compressor Pedal guitar what’s hot existing
Line 6 POD Go Guitar Multi-effects Floor Processor guitar what’s hot existing
MXR M222 Talk Box Pedal guitar what’s hot existing
Pedaltrain Classic Jr SC 18x12.5 Pedalboard with Soft Case guitar what’s hot existing
Pedaltrain Nano+ 18x5 Pedalboard with Soft Case guitar what’s hot existing
Pro Co Rat 2 Distortion / Fuzz / Overdrive Pedal guitar what’s hot existing
Strymon Iridium Amp & IR Cab Pedal guitar what’s hot existing
TC Electronic Ditto+ Looper Pedal guitar what’s hot existing
Gretsch G6136T Limited-edition Falcon Hollowbody Electric Guitar - Two Tone Copper/Sahara Metallic guitar new arrivals new
Line 6 HX Stomp XL Guitar Multi-effects Floor Processor guitar new arrivals new
Line 6 POD Go Wireless Guitar Multi-effects Floor Processor guitar new arrivals new
PRS Limited Edition SE Parlor P20E Acoustic-electric Guitar - Antique White guitar new arrivals new
Universal Audio UAFX Astra Modulation Machine Pedal guitar new arrivals new
Korg MS-20 FS Full-size MS-20 Synthesizer (White) keyboard new arrivals new
Black Lion Audio Revolution 2x2 USB Audio Interface studio new arrivals new
Kali Audio LP-6 6.5 inch Powered Studio Monitor Pair studio new arrivals new
Kali Audio LP-8 8 inch Powered Studio Monitor Pair studio new arrivals new
KRK ROKIT 5 G4 5 inch Powered Studio Monitor Pair studio new arrivals new
MOTU UltraLite-mk5 18x22 USB Audio Interface studio new arrivals new
Novation Circuit Tracks Groovebox studio new arrivals new
Yamaha HS5 5 inch Powered Studio Monitor Pair - White studio new arrivals new
Yamaha HS7 6.5 inch Powered Studio Monitor Pair - Black studio new arrivals new
Yamaha HS8 8 inch Powered Studio Monitor Pair - White studio new arrivals new
Yamaha HS8 8-inch Powered Studio Monitor Pair - Black studio new arrivals new
D’Addario EXP16 - Coated Phosphor Bronze Light Acoustic Strings 4-pack guitar top deals new
D’Addario Humidipak Standard Replacement 9-pack guitar top deals new
Line 6 Relay G10 Digital Wireless Guitar System guitar top deals new
Martin Authentic Acoustic Superior Performance Guitar Strings - 92/8 Phosphor Bronze Medium 3-pack guitar top deals new
Snark Silver Snark Clip-on Chromatic Tuner 3-pack guitar top deals new
String Swing CC01K Guitar Keeper Wall Mount Guitar Hanger 2-pack - Black Walnut guitar top deals new
AKG K175 2-pack Closed-back On-ear Foldable Headphones studio top deals new
AKG K175 4-Pack Closed-back On-ear Foldable Headphones studio top deals new
AKG K175 Closed-Back On-Ear Foldable Headphones studio top deals new
AKG P420 Large-diaphragm Condenser Microphone studio top deals new
Furman SS-6B 6-outlet Surge Suppressor Strip (2-pack) studio top deals new
On-Stage Stands MS7701B Euro Boom Microphone Stand 5-pack Bundle with 5 Mic Cables studio top deals new
PreSonus Eris E3.5 3.5 inch Powered Studio Monitors studio top deals new
Pro Co BP-10 Excellines Balanced Patch Cable TRS Male to TRS Male 8-pack - 10 foot studio top deals new
Pro Co BP-5 Excellines Balanced Patch Cable TRS Male to TRS Male 8-pack - 5 foot studio top deals new
Sennheiser e 825-S Dynamic Vocal Microphone - Pair studio top deals new
TC Electronic Ditto+ Looper Pedal guitar what’s hot new
Beyerdynamic DT 770 Pro 80 ohm Closed-back Studio Mixing Headphones studio what’s hot new
Cloud Microphones CL-1 Cloudlifter 1-channel Mic Activator studio what’s hot new
Focusrite Scarlett 2i2 3rd Gen USB Audio Interface studio what’s hot new
Focusrite Scarlett Solo 3rd Gen USB Audio Interface studio what’s hot new
Furman SS-6B 6-outlet Surge Suppressor Strip studio what’s hot new
Furman SS-6B 6-outlet Surge Suppressor Strip (2-pack) studio what’s hot new
JBL 305P MkII 5-inch Powered Studio Monitor studio what’s hot new
JBL 305P MkII 5-inch Powered Studio Monitor Pair studio what’s hot new
PreSonus Eris E3.5 3.5 inch Powered Studio Monitors studio what’s hot new
Rode NT1-A Large-Diaphragm Condenser Microphone studio what’s hot new
Sennheiser HD 280 Pro Closed-Back Studio and Live Monitoring Headphones studio what’s hot new
Shure SM57 Cardioid Dynamic Instrument Microphone studio what’s hot new
Shure SM58 Cardioid Dynamic Vocal Microphone studio what’s hot new
Shure SM7B Cardioid Dynamic Vocal Microphone studio what’s hot new
Sony MDR-7506 Closed-Back Professional Headphones studio what’s hot new

Recommender System Analysis

# Purchase history summary
tmp_purch <- purch %>% group_by(category) %>%
  summarise(count = n()) %>%
  mutate(type = "purchased")

# Recommended products summary
tmp_existing <- recommend %>%
  filter(customer == "existing") %>%
  group_by(category) %>%
  summarize(count = n()) %>%
  mutate(type = "recommended")

# Merge together for plot
merged_existing <- tmp_purch %>%
  bind_rows(tmp_existing)

# Plot existing customer recommendations
merged_existing %>% ggplot() +
  geom_bar(aes(x = category, y = count, fill = type), stat = "identity", position = "dodge", width = 0.5) +
  ggtitle("Existing customer - recommended products vs. order history")

# Recommended products summary
tmp_new <- recommend %>%
  filter(customer == "new") %>%
  group_by(category) %>%
  summarize(count = n()) %>%
  mutate(type = "recommended")

# Merge together for plot
merged_new <- tmp_purch %>%
  bind_rows(tmp_new)

# Plot existing customer recommendations
merged_new %>% ggplot() +
  geom_bar(aes(x = category, y = count, fill = type), stat = "identity", position = "dodge", width = 0.5) +
  ggtitle("New customer - recommended products vs. order history")

Based on the above analysis, it doesn’t appear that Sweetwater’s recommender system is related to order history at all. A few alternate ideas came to mind.

  • Frequently bought together

I spot-checked a few items I bought to see if any of those items were frequently bought together with any of the recommended items, but this also didn’t prove to be the case.

  • Random?

It doesn’t appear to be random; otherwise a new customer would be equally likely to be recommended the same products as I was.

  • Inventory dump

Because there was some overlap with new customers, my guess is that at least some of the recommendations were based on inventory they’re trying to unload.

  • Similar cost

I also thought it might be by amount spent, but the total I’ve spent on studio gear far outweighs anything in the other categories (I’m not including the amounts in the table, because I was mortified at how much I’ve blown on gear over the past few years).

  • Clustering/collaborative filtering

My best guess is that they use some kind of poorly implemented clustering or collaborative filtering system, and I happen to be situated next to a customer who likes crappy gear (or I happen to have been assigned to the “crappy gear cluster”). Or maybe it’s trying to give me a subtle hint that I like crappy gear.

  • Buggy code?

The fact that they didn’t recommend a single product from the drum, keyboard, or studio category–and that all recommended products were from the guitar category–tells me that maybe there is a glitch in their code that may require the attention of a data scientist.

Any way I looked at it, it wasn’t obvious to me how they were recommending products – other than “poorly.”

Recommendation

Because it was difficult to discern which recommender system they use, one recommendation would be to at least select a few products related to order history, possibly switching to a search-based system that uses item category from the customer’s order history.

An additional recommendation would be to place recommendation on a single page, have fewer of them, and not require a user to scroll as much to view them. I think a user is typically pretty lazy when it comes to looking for things; if it doesn’t jump out at him, I’d bet the chances he’d click on something drop exponentially.