This happens when trying to install a new dependency and there is not enough memory, so you can raise the memory (in this case to 3GB)  temporarily using :

```cmd
php -d memory_limit=3G C:\ProgramData\ComposerSetup\bin\composer.phar require  excelwebzone/r
```
Check the actual memory limit with:

```cmd
php -r "echo ini_get('memory_limit').PHP_EOL;"
```