Longitudinal Concordance Correlation Function Based on Variance Components: An Application in Fruit Color Analysis

Autor(es)

Oliveira, Thiago de Paula ^[1] ; Hinde, John ^[2] ; Zocchi, Silvio Sandoval ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Ciencias Exatas, Escola Super Agr Luiz de Queiroz, Av Padua Dias 11, BR-13418900 Piracicaba, SP - Brazil

^[2] Natl Univ Ireland, Sch Math Stat & Appl Math, Univ Rd, Galway - Ireland

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF AGRICULTURAL BIOLOGICAL AND ENVIRONMENTAL STATISTICS; v. 23, n. 2, p. 233-254, JUN 2018.
• Citações Web of Science: 0

Resumo

The maturity stages of papaya fruit based on peel color are frequently characterized from a sample of four points on the equatorial region measured by a colorimeter. However, this procedure may not be suitable for assessing the papaya's overall mean color and an alternative proposal is to use image acquisition of the whole fruit's peel. Questions of interest are whether a sample on the equatorial region can reproduce a sample over the whole peel region and if the colorimeter can compete with a scanner, or digital camera, in measuring the mean hue over time. The reproducibility can be verified by using the concordance correlation for responses measured on a continuous scale. Thus, in this work we propose a longitudinal concordance correlation (LCC), based on a mixed-effects regression model, to estimate agreement over time among pairs of observations obtained from different combinations between measurement method and sampled peel region. The results show that the papaya's equatorial region is not representative of the whole peel region, suggesting the use of image analysis rather than a colorimeter to measure the mean hue. Moreover, in longitudinal studies the LCC can suggest over which period the two methods are likely to be in agreement and where the simpler colorimeter method could be used. The performance of the LCC is evaluated using a small simulation study. Supplementary materials accompanying this paper appear online. (AU)

• Processo FAPESP: 10/16955-1 - Utilização de scanners de mesa como dispositivos para a medição da cor da casca e polpa de mamões (Carica papaya l.) Sunrise Solo
• Beneficiário: Thiago de Paula Oliveira
• Linha de fomento: Bolsas no Brasil - Iniciação Científica