[QUESTION] Load multiple files from CSV?

[dneagoy]

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Hi, I'm new to JavaScript so apologies if this question is obvious.

I'm attempting to load two CSV files to two dataframes within the same promise. I read through your comments on Issue #50 and that was very helpful. My question is whether it's possible to load two CSV files in the same promise. If so, can you provide an example?

I'm including a link and example below of what I'm hoping to accomplish. Thanks

Additional context
I've done some reading and see that D3 loads multiple CSV's to a promise as shown below per this link : http://learnjsdata.com/read_data.html

`Promise.all([
  d3.csv("/data/cities.csv"),
  d3.tsv("/data/animals.tsv")
]).then(function(data) {
  console.log(data[0][0])  // first row of cities
  console.log(data[1][0])  // first row of animals
});`

[Gmousse]

Hi @dneagoy !
Thank you for your question.
Don't worry, a lot of users are coming from R or Python.

There is different ways to achieve that point.

Example:

The best and easier way with concurrency by using Promise.all:

const dfjs = require("dataframe-js");

Promise.all([
  dfjs.DataFrame.fromCSV("/file-1.csv"),
  dfjs.DataFrame.fromCSV("/file-2.csv")
]).then(dfs => {
  const df = dfs.reduce((df1, df2) => df1.union(df2));
  df.show();
});

Or sequentially with a new promise:

new Promise((resolve, reject) => {
  dfjs.DataFrame.fromCSV("/file-1.csv")
    .then(df1 => {
      dfjs.DataFrame.fromCSV("/file-2.csv")
        .then(df2 => resolve([df1, df2]))
        .catch(reject);
    })
    .catch(reject);
}).then(dfs => {
  const df = dfs.reduce((df1, df2) => df1.union(df2));
  df.show();
});

There is of course other possibilities.

I hope it will help you.

Feel free to close if it resolved.

[dneagoy]

Perfect, that's exactly what I was looking for. Thanks for your help @Gmousse !

[feiyu-london]

I also read issue #50 and find it quite helpful.

Then I come to the same issue as above. My work requires pulling in a few different tables and put them together after some operations.

My solution is not as sophisticated as above. I simply nest a few .fromCVS to get around the issue.

.fromCSV(csv no.1) {to df1;
.fromCSV(csv no.2) {to df2;
.fromCSV(csv no.3) {to df3;
[operating on df1, df2 and df3 ...]
}
}
};

sorry I did not really write the syntax but hope the above can make sense.