split string into multiple parts given in a vector

Question

R Gurus, I am struggling to find an efficient way to split a string into multiple parts given in a vector.

In the following example, I have few cryptocurrencies' pairs from BINANCE exchange. I want to split each pair into two separate parts given in symbol column in top100 data frame.

library(dplyr)
library(jsonlite)
library(RCurl)

top100 <- data.frame(fromJSON(getURL(paste0('https://api.coinmarketcap.com/v1/ticker/?start=0&limit=100'))))

markets <- data.frame(pairs = c("NEOBTC","EOSETH","VENETH","ELFETH","ICXETH","BNBETH","NEOETH",
                                "TRXETH","QTUMETH","DASHETH","XRPETH" ,"ETHUSDT","LTCUSDT","ADAETH",
                                "XMRETH","ZECETH","IOTAETH","NEOUSDT","BNBUSDT","XLMBNB","LSKBNB"), 
                      symbol1 = NA,
                      symbol2 = NA)

markets$symbol1 <- substr(markets$pairs, 1,3) markets$symbol2 <- substr(markets$pairs, 4,6)

markets$symbol1 %in% top100$symbol markets$symbol2 %in% top100$symbol

One naive way do that is to take first three characters of the ticker as symbol1 and last three characters as symbol2, some tickers have more than three characters like DASH.

The JSON response doesn't seem to imply pairing to me. It just looks like a list of cryptocurrencies. — Tim Biegeleisen
– Tim Biegeleisen, Commented Jan 15, 2018 at 2:05
Please try this: top100 <- data.frame(jsonlite::fromJSON(RCurl::getURL(paste0('api.coinmarketcap.com/v1/ticker/?start=0&limit=100')))) — M.Qasim
– M.Qasim, Commented Jan 15, 2018 at 2:08
This JSON query fetches a list of top 100 cryptocurrencies from coinmarketcap.com — M.Qasim
– M.Qasim, Commented Jan 15, 2018 at 2:08
Pairs are download are historic data of recent trades. All trade-able pairs on BINANCE are listed on binance.com — M.Qasim
– M.Qasim, Commented Jan 15, 2018 at 2:11

Onyambu · Accepted Answer · 2018-01-15 10:03:39Z

You can try the following code:

grep("\\w\\s\\w",sapply(paste0("(",top100$symbol,"$)"),
                    sub,"\\3 \\1",a<-markets$pairs),value = T)%>%
                    {.[match(a,sub("\\s","",.))]}%>%
                    strsplit(.,"\\s")%>%do.call(rbind,.)%>%
                    {setNames(as.data.frame(.),paste0("Symbols",1:2))}

You can also try:

sub(paste0("(",top100$symbol,")$",collapse = "|"),"",a<-markets$pairs)%>%
{cbind.data.frame(Symbols1=.,Symbols2=sub(paste0("^(",.,")",collapse = "|"),"",a))}

Both the codes above give:

      Symbols1 Symbols2
1       NEO      BTC
2       EOS      ETH
3       VEN      ETH
4       ELF      ETH
5       ICX      ETH
6       BNB      ETH
7       NEO      ETH
8       TRX      ETH
9      QTUM      ETH
10     DASH      ETH
11      XRP      ETH
12      ETH     USDT
13      LTC     USDT
14      ADA      ETH
15      XMR      ETH
16      ZEC      ETH
17     IOTA      ETH
18      NEO     USDT
19      BNB     USDT
20      XLM      BNB
21      LSK      BNB

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