Need to format an array of objects in a different way

Question

I have a matrix response array:

matrixArray = [
                {Responded: 1, RowName: row1, ColName: col1},
                {Responded: 2, RowName: row1, ColName: col2},
                {Responded: 0, RowName: row1, ColName: col3},
                {Responded: 0, RowName: row2, ColName: col1},
                {Responded: 0, RowName: row2, ColName: col2},
                {Responded: 1, RowName: row2, ColName: col3},
                {Responded: 1, RowName: row3, ColName: col1},
                {Responded: 0, RowName: row3, ColName: col2},
                {Responded: 1, RowName: row3, ColName: col3},
                ...
                ...
              ];

It tells that how many times a column has been responded for a row. I need above array of objects in the following format:

matrixArray = [
                {
                  RowName: row1,
                  col1: 1,           //Here '1' is no. of times column responded
                  col2: 2,
                  col3: 0
                },
                {
                  RowName: row2,
                  col1: 0,
                  col2: 0,
                  col3: 1
                },
                {
                  RowName: row3,
                  col1: 1,
                  col2: 0,
                  col3: 1
                },
              ];

I am using TypeScript for this. Thanks.

You can edit your question. Also, as I said above, you're supposed to show what you tried before people help you. At least share what your approach is and what you can't figure out. — Jeto
– Jeto, Commented Jan 20, 2019 at 9:23
I've had an answer ready, I'm going to post it anyway before I lose track of it. Please make an effort to show your attempts next time. — Jeto
– Jeto, Commented Jan 20, 2019 at 17:55
Apologies @Jeto but had some connection probs so not able to post my attempts. I was making use of forEach and .filter on the array. My plan was to get the rows first in a different array, and then push the columns respective to it. But that plan didn't work actually. — Mr. A
– Mr. A, Commented Jan 21, 2019 at 2:58

Jeto · Accepted Answer · 2019-01-21 07:53:02Z

You can make use of Array.reduce and Object.values to obtain the desired result:

const matrixArray = [
  {Responded: 1, RowName: 'row1', ColName: 'col1'},
  {Responded: 2, RowName: 'row1', ColName: 'col2'},
  {Responded: 0, RowName: 'row1', ColName: 'col3'},
  {Responded: 0, RowName: 'row2', ColName: 'col1'},
  {Responded: 0, RowName: 'row2', ColName: 'col2'},
  {Responded: 1, RowName: 'row2', ColName: 'col3'},
  {Responded: 1, RowName: 'row3', ColName: 'col1'},
  {Responded: 0, RowName: 'row3', ColName: 'col2'},
  {Responded: 1, RowName: 'row3', ColName: 'col3'}
];

const result = Object.values(matrixArray.reduce((result, entry) => {
  if (!(entry.RowName in result)) {
    result[entry.RowName] = {RowName: entry.RowName};
  }
  if (!(entry.ColName in result[entry.RowName])) {
    result[entry.RowName][entry.ColName] = 0;
  }
  result[entry.RowName][entry.ColName] += entry.Responded;
  return result;
}, {}));

console.log(result);

Note that I didn't type the variables to make it runnable here, feel free to do so since you're using Typescript.

Explanation:

Array.reduce loops over the array and builds a RowName => {RowName, col1, col2, col3} map (object) by incrementing by the corresponding Responded amount on each iteration),
Object.values then transforms that back into an array.

adiga · Accepted Answer · 2019-01-21 08:16:26Z

1

You can use reduce and Object.values like this:

const matrixArray = [{Responded:1,RowName:'row1',ColName:'col1'},{Responded:2,RowName:'row1',ColName:'col2'},{Responded:0,RowName:'row1',ColName:'col3'},{Responded:0,RowName:'row2',ColName:'col1'},{Responded:0,RowName:'row2',ColName:'col2'},{Responded:1,RowName:'row2',ColName:'col3'},{Responded:1,RowName:'row3',ColName:'col1'},{Responded:0,RowName:'row3',ColName:'col2'},{Responded:1,RowName:'row3',ColName:'col3'}]

const merged = matrixArray.reduce((acc, {Responded,RowName,ColName}) => {
       acc[RowName] = acc[RowName] || {RowName};
       acc[RowName][ColName] = (acc[RowName][ColName] + Responded) || Responded;
       return acc;
   }, {});

const output = Object.values(merged);
console.log(output)

Here's a shorter version of the above code:

const matrix = [{Responded:1,RowName:'row1',ColName:'col1'},{Responded:2,RowName:'row1',ColName:'col2'},{Responded:0,RowName:'row1',ColName:'col3'},{Responded:0,RowName:'row2',ColName:'col1'},{Responded:0,RowName:'row2',ColName:'col2'},{Responded:1,RowName:'row2',ColName:'col3'},{Responded:1,RowName:'row3',ColName:'col1'},{Responded:0,RowName:'row3',ColName:'col2'},{Responded:1,RowName:'row3',ColName:'col3'}],
  
output = Object.values(matrix.reduce((a, {Responded,RowName,ColName}) => (
    (a[RowName] = a[RowName] || {RowName})[ColName] = Responded, a), {}));

console.log(output);

edited Jan 21, 2019 at 8:16

answered Jan 20, 2019 at 19:10

adiga

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3 Comments

adiga Over a year ago

@Mr.A just a heads up: The accepted answer has the column names hard coded inside the reduce. It won't work if there's another column named col4.

Jeto Over a year ago

@adiga Fixed that--I did suppose these columns were specific anyway. As a note, this one doesn't do well if several entries have the same RowName / ColName (in which case it would be logical to increment the Responded count each time). Not sure this is possible though (probably not!)

adiga Over a year ago

@Jeto Yeah, I'd have to add a ternary in between to handle that. Looking at OP's data, I assumed there won't be any duplicates for rows and columns.

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