# Dynamic Metrics Selection
> Learn how to create measures that adapt based on context or user input
:::tip knowledge checkpoint
A grasp of these concepts will help you understand this documentation better:
- [Parameter Fields](/docs/modeling/param-fields)
- [AQL Expression](/reference/aql/expression)
- [Measure](/docs/model-fields#measures)
:::
## Introduction
Using [param fields](/docs/modeling/param-fields), we can build charts with dropdown that allow users to change the metric dynamically.
## Dynamic Metrics Selection
Assuming that you have a model with 3 metrics: `total_orders`, `revenue`, and `total_users`. You want to build a dashboard that let user pick which measure to be used in your report.
```typescript
Model sales_model {
measure total_orders { }
measure revenue { }
measure total_users { }
}
```
This can be implemented using [Parameter Field](/docs/modeling/param-fields) and [AQL Expression](/reference/aql/expression)
### Step 1: Create a Parameter Field
First, create a [Parameter Field](/docs/modeling/param-fields) in the model.
```typescript
Model sales_model {
measure total_orders { }
measure revenue { }
measure total_users { }
//highlight-start
param metric_selector {
label: 'Metric Selector'
type: 'text'
allowed_values: ['Total Orders', 'Revenue', 'Total Users']
}
//highlight-end
}
```
### Step 2: Create a Dynamic Metric field
Create a Dynamic Metric that changes based on the selected parameter value.
```ts
Model sales_model {
measure total_orders { }
measure revenue { }
measure total_users { }
param metric_selector { }
//highlight-start
measure dynamic_metric {
definition: @aql case(
when: 'Total Orders' in sales_model.measure_selector
, then: sales_model.total_orders
, when: 'Revenue' in sales_model.measure_selector
, then: sales_model.revenue
, when: 'Total Users' in sales_model.measure_selector
, then: sales_model.total_users
) ;;
}
//highlight-end
}
```
### Step 3: Use `Dynamic Metrics` in the report
In the report, you can use `Dynamic Metrics` with another dimension.
### Step 4: Use Parameter Field in the dashboard filter
In the dashboard filter, you can use `Measure Selector` Parameter Field to dynamically choose which measure to use in the report.
## Advanced: Metrics selection at Dataset level
If your metrics are defined at the dataset level, we recommend **creating a dedicated model to store your parameter fields**. While you can technically place parameter fields in any existing model, having a dedicated model gives you a single, predictable place to manage them.
1. **Create a separate model to contain the `param`**
```tsx
Model param_model {
type: 'query' // can be either `table` or `query` model
query: @sql select 1 ;; // Dummy query
//highlight-start
param metric_selector {
label: 'Metric Selector'
type: 'text'
allowed_values: ['Revenue', 'Total Orders', 'Total Users']
}
//highlight-end
}
```
2. **Add the `param_model` to the Dataset and define the `dynamic_metrics` at the dataset level**
```tsx
Dataset ecommerce {
//highlight-next-line
models: [countries, cities, users, orders, param_model]
relationships: [ ]
metric revenue { }
metric total_orders { }
metric total_users { }
//highlight-start
metric dynamic_metrics {
label: 'Dynamic Metrics'
type: 'number'
definition: @aql
case(
when: 'Revenue' in param_model.metric_selector
, then: revenue
, when: 'Total Orders' in param_model.metric_selector
, then: total_orders
, when: 'Total Users' in param_model.metric_selector
, then: total_users
)
;;
}
//highlight-end
}
```