예제: 로그 회귀

logfit

logfit 함수를 사용하여 다음 로그 방정식에 데이터를 맞춥니다.

1. 다음 행렬을 정의합니다.

2. 추측값 벡터를 정의합니다.

ln 함수는 양수에 대해서만 정의됩니다. ln을 계산하는 데 필요한 경우 둘째 매개변수에 의해 x 데이터가 이동합니다. x 데이터가 음수이면 둘째 추측값이 양수여야 하고 x 값을 양의 축으로 이동할 만큼 충분히 커야 합니다.

경우에 따라서는 가능한 최적합을 구하기 위해 추측값을 조정해야 할 수도 있습니다. 첫째 값은 데이터의 높이와 부호를 대략적으로 나타내고, 둘째 값은 가로 오프셋을 반영하고, 셋째 값은 세로 오프셋을 반영합니다. 데이터를 먼저 도표화하여 추측값을 확인할 수 있습니다.

3. logfit 함수를 사용하여 로그 적합식의 매개변수를 구합니다.

둘째 매개변수가 매우 작습니다. 이 경우 logfit 대신 lnfit 함수를 사용하는 것도 좋은 방법입니다.

4. 데이터와 로그 적합식을 도표화합니다.

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상관 계수에서 알 수 있듯이 적합도가 거의 완벽합니다.

lnfit

lnfit 함수를 사용하여 다음 로그 방정식에 데이터를 맞춥니다.

1. lnfit을 호출하여 매개변수 a와 b를 구합니다.

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2. 데이터와 적합식을 도표화합니다.

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3. 상관 계수를 계산합니다.

계산 결과가 logfit 함수를 사용하여 얻은 상관 계수와 매우 비슷하다는 것을 알 수 있습니다.