Protobi

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## Adding code to your project

Protobi lets you make programmatic changes to your survey data directly within the platform. There are two ways to do this: **Pre-calculate**, which runs automatically every time your project loads, and **Data process**, which you run manually when needed.

For small modifications, Pre-calculate is a good place to start.

---

## Pre-calculate

Go to your project's Settings and open the **Pre-calculate** tab. You'll see a single line of code by default:

```js
return rows;
```

This is the most basic data process. `rows` represents your project's primary dataset, and this line simply returns it as-is. Protobi executes whatever is in Pre-calculate before your project finishes loading, so it's best suited for simple, lightweight operations that won't slow things down.

### Try it out

The example below creates a pop-up message showing the number of respondents in your dataset. Copy it into Pre-calculate and hit **Save**.

```js
var message = "This dataset has " + rows.length + " respondents";
alert(message);

return rows;
```
The message will appear each time the project is opened or the page is reloaded.
<img src="/uploads/upload/image/5200/direct/1596223342306-alert.gif" style="width: 1000px;" class="fr-fic fr-dib" alt="Animation showing the Pre-Calculate code saved and the resulting alert pop-up message displaying the text 'This dataset has 100 respondents' when the project is opened in the browser.">

### Summing values across columns

A common use of Pre-calculate is creating a derived variable that adds together several columns from the same row. For example, suppose you want to total the number of patients across all products for **Q2**.

You can create a new variable `Q2_sum` like this:

```js
rows.forEach(function(row) {
    row.Q2_sum = (+row.Q2_1) + (+row.Q2_2) + (+row.Q2_3);
});

return rows;
```

The `forEach` loop runs this calculation for every respondent in the dataset.

**A note on the `+` operator.** Protobi stores your data as a CSV, which means all values are text strings — the string `"2"` rather than the number `2`. This matters because JavaScript handles addition differently depending on the type: two numbers give you a sum (`2 + 2 = 4`), but two strings give you concatenation (`"2" + "2" = "22"`). Prefixing each value with `+` forces JavaScript to treat it as a number.

### Using your new variable

Once created, `Q2_sum` will have numeric values that you can [bin into ranges](/edit-access/bin-numeric-values).

Note that variables created in Pre-calculate are not added to your dashboard automatically — you'll need to create the element manually by clicking the **+** button under a group or tab and referencing the variable key (e.g. `Q2_sum`).

---

## Data process

For more substantial data work, you can create a dedicated process in the **Data** tab of your project's Settings. Unlike Pre-calculate, data processes are run manually and are better suited for heavier operations like combining multiple data tables or defining variables with complex logic.

### Return a data table

If your project has a data table with the key `main`, the simplest process just returns it:

```js
var rows = data["main"];

return rows;
```

### Combine survey waves

A common use case is stacking multiple waves of data into a single dataset. If your project has separate data tables for each wave, you can combine them like this:

```js
var W1 = data["wave1"];
var W2 = data["wave2"];
var W3 = data["wave3"];
var W4 = data["wave4"];

var rows = Protobi.stack_rows([W1, W2, W3, W4]);

return rows;
```

### Define new variables with conditional logic

You can also create new variables based on conditions. The example below creates a `therapy_use` variable derived from a respondent's answers to Q1 and Q5_1:

```js
var rows = data["main"];

rows.forEach(function(row) {
    if (row.Q1 == 1 || row.Q5_1 == 1) row.therapy_use = 1; // High use
    else row.therapy_use = 0; // Low use
});

return rows;
```

We recommend assigning integer values to new variables and using [Value formats](/edit-access/formatting) to label them — this is consistent with how most survey data is programmed.

**Remember:** After editing a data process, click **Save** then **Run**. To use the result as your project's primary data, you'll also need to mark it as **Primary**. Data processes are project-specific, so your implementation may look slightly different from the examples above.

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