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Spreadsheet Processing in Mathematica

Mathematica is a software system for mathematics and scientific computing. It supports command-line tools and JavaScript extensions.

SheetJS is a JavaScript library for reading and writing data from spreadsheets.

This demo uses SheetJS to pull data from a spreadsheet for further analysis within Mathematica. We'll explore how to run an external tool to generate CSV data from opaque spreadsheets and parse the data from Mathematica.

note

This demo was last tested in 2023 August 21 in Mathematica 13.2.1.

Integration Details​

The SheetJS NodeJS module can be loaded in NodeJS scripts, including scripts invoked using the "NodeJS" mode of the ExternalEvaluate1 Mathematica function.

However, the current cross-platform recommendation involves a dedicated command line tool that leverages SheetJS libraries to to perform spreadsheet processing.

External Engines​

The following diagram depicts the workbook waltz:

Mathematica

NodeJS can be activated from Mathematica using RegisterExternalEvaluator2. Once activated, JavaScript code can be run using ExternalEvaluate3. If the NodeJS code returns CSV data, ImportString4 can generate a Dataset5.

SheetJS

For a file residing on the filesystem, the SheetJS readFile function6 can generate a workbook object. The exact location can be determined by printing require("process").cwd()7 in ExternalEvaluate:

In[1]:= ExternalEvaluate["NodeJS", "require('process').cwd()"]
Out[1]= "C:\Users\Me\Documents"

After pulling the first worksheet8, the SheetJS sheet_to_csv function9 generates a CSV string.

Complete Function

The following function reads a file, parses the first worksheet and returns a Dataset object assuming one header row.

Complete Function
(* Import file stored in the Documents folder (e.g. C:\Users\Me\Documents) *)
SheetJSImportFileEE[filename_]:=Module[{csv}, (
  (* This was required in local testing *)
  RegisterExternalEvaluator["NodeJS","C:\\Program Files\\nodejs\\node.exe"];

  (* Generate CSV from first sheet *)
  csv:=ExternalEvaluate["NodeJS", StringJoin[
    (* module installed in home directory *)
    "var XLSX = require('xlsx');",
    (* read specified filename *)
    "var wb = XLSX.readFile('",filename,"');",
    (* grab first worksheet *)
    "var ws = wb.Sheets[wb.SheetNames[0]];",
    (* convert to CSV *)
    "XLSX.utils.sheet_to_csv(ws)"
  ]];

  (* Parse CSV into a dataset *)
  ImportString[csv, "Dataset", "HeaderLines"->1];
)]
How to run the example (click to hide)
note

This example was last tested on 2023 September 13 with Mathematica 13.3.

0) Install NodeJS. When the demo was tested, version 18.14.1 was installed.

1) Install dependencies in the Home folder (~ or $HOME or %HOMEPATH%):

npm i --save https://cdn.sheetjs.com/xlsx-0.20.0/xlsx-0.20.0.tgz [email protected]

2) Open a new Mathematica Notebook and register NodeJS. When the example was tested in Windows, the commands were:

RegisterExternalEvaluator["NodeJS","C:\\Program Files\\nodejs\\node.exe"]
FindExternalEvaluators["NodeJS"]

The second argument to RegisterExternalEvaluator should be the path to the node or node.exe binary.

If NodeJS is registered, the value in the "Registered" column will be "True".

4) To determine the base folder, run require("process").cwd() from NodeJS:

ExternalEvaluate["NodeJS", "require('process').cwd()"]

5) Download pres.numbers and move the file to the base folder as shown in the previous step.

6) Copy and evaluate the "Complete Function" in the previous codeblock.

7) Run the function and confirm the result is a proper Dataset:

SheetJSImportFileEE["pres.numbers"]

Command-Line Tools​

The "Command-Line Tools" demo creates xlsx-cli, a command-line tool that reads a spreadsheet file and generates CSV rows from the first worksheet.

ExternalEvaluate10 can run command-line tools and capture standard output. The following snippet processes ~/Downloads/pres.numbers and pulls CSV data into a variable in Mathematica:

cmd = "/usr/local/bin/xlsx-cli ~/Downloads/pres.numbers"
csvdata = ExternalEvaluate["Shell" -> "StandardOutput", cmd];

ImportString11 can interpret the CSV data as a Dataset12. Typically the first row of the CSV output is the header row. The HeaderLines13 option controls how Mathematica parses the data:

data = ImportString[csvdata, "Dataset", "HeaderLines" -> 1]

The following diagram depicts the workbook waltz:

Complete Demo​

This demo was tested in macOS. The path names will differ in other platforms.

1) Create the standalone xlsx-cli binary14:

cd /tmp
npm i --save https://cdn.sheetjs.com/xlsx-0.20.0/xlsx-0.20.0.tgz exit-on-epipe commander@2
curl -LO https://docs.sheetjs.com/cli/xlsx-cli.js
npx nexe -t 14.15.3 xlsx-cli.js

2) Move the generated xlsx-cli to a fixed location in /usr/local/bin:

mkdir -p /usr/local/bin
mv xlsx-cli /usr/local/bin/

Reading a Local File​

3) In a new Mathematica notebook, run the following snippet:

SheetJSImportFile[x_] := ImportString[Block[{Print}, ExternalEvaluate[
  "Shell" -> "StandardOutput",
  "/usr/local/bin/xlsx-cli " <> x
]], "Dataset", "HeaderLines" -> 1]

4) Download https://sheetjs.com/pres.numbers and save to Downloads folder:

cd ~/Downloads/
curl -LO https://sheetjs.com/pres.numbers

5) In the Mathematica notebook, run the new function. If the file was saved to the Downloads folder, the path will be "~/Downloads/pres.numbers" in macOS:

data = SheetJSImportFile["~/Downloads/pres.numbers"]

The result should be displayed in a concise table.

Reading from a URL​

FetchURL15 downloads a file from a specified URL and returns a path to the file. This function will be wrapped in a new function called SheetJSImportURL.

6) In the same notebook, run the following:

Needs["Utilities`URLTools`"];
SheetJSImportURL[x_] := Module[{path},(
  path = FetchURL[x];
  SheetJSImportFile[path]
)];

7) Test by downloading the test file in the notebook:

data = SheetJSImportURL["https://sheetjs.com/pres.numbers"]
  1. See the ExternalEvaluate Node.js example in the Mathematica documentation.↩
  2. See RegisterExternalEvaluator in the Mathematica documentation.↩
  3. See ExternalEvaluate in the Mathematica documentation.↩
  4. See ImportString in the Mathematica documentation.↩
  5. A Dataset will be created when using the "Dataset" element in ImportString↩
  6. See readFile in "Reading Files"↩
  7. See process.cwd() in the NodeJS documentation.↩
  8. The Sheets and SheetNames properties of workbook objects are described in "Workbook Object"↩
  9. See sheet_to_csv in "CSV and Text"↩
  10. See ExternalEvaluate in the Mathematica documentation.↩
  11. See ImportString in the Mathematica documentation.↩
  12. A Dataset will be created when using the "Dataset" element in ImportString↩
  13. See HeaderLines in the Mathematica documentation.↩
  14. See "Command-line Tools" for more details.↩
  15. Mathematica 11 introduced new methods including URLRead.↩