Low-Fat Waldorf Salad

2 small apples, cored and diced
1 cup seedless grapes, halved
1 cup plain yogurt
1 celery stalk, diced
1/4 cup chopped walnuts
2 Tablespoons raisins
1 1/2 teaspoon fresh lime juice
Cinnamon to taste (opt.)
Mix all together and serve immediately.