init_param

init_Zhang

init_AG

init_AG2

init_Beck

init_Elmore

init_Gu

init_Klos

Initialize parameters of double logistic function

internal

The merits of 'TIMESAT' and 'phenopix' are adopted. Besides, a simple and
growing season dividing method and a practical snow elimination method
based on Whittaker were proposed. 7 curve fitting methods and 4 phenology
extraction methods were provided. Parameters boundary are considered for
every curve fitting methods according to their ecological meaning.
And 'optimx' is used to select best optimization method for different
curve fitting methods.
Reference:
Kong, D., (2020). R package: A state-of-the-art Vegetation Phenology extraction
package, phenofit version 0.3.1, <doi:10.5281/zenodo.5150204>;
Kong, D., Zhang, Y., Wang, D., Chen, J., & Gu, X. (2020). Photoperiod Explains
the Asynchronization Between Vegetation Carbon Phenology and Vegetation Greenness
Phenology. Journal of Geophysical Research: Biogeosciences, 125(8), e2020JG005636.
<doi:10.1029/2020JG005636>;
Kong, D., Zhang, Y., Gu, X., & Wang, D. (2019). A robust method for reconstructing
global MODIS EVI time series on the Google Earth Engine.
ISPRS Journal of Photogrammetry and Remote Sensing, 155, 13–24;
Zhang, Q., Kong, D., Shi, P., Singh, V.P., Sun, P., 2018. Vegetation phenology
on the Qinghai-Tibetan Plateau and its response to climate change (1982–2013).
Agric. For. Meteorol. 248, 408–417. <doi:10.1016/j.agrformet.2017.10.026>.

Dongdong Kong

phenofit

Extract Remote Sensing Vegetation Phenology

Mingzhong Xiao

Yongqiang Zhang

Xihui Gu

Jianjian Cui

init_param function

<dl><dt>y</dt>
<dd>Numeric vector, vegetation index time-series</dd>
<dt>t</dt>
<dd>Numeric vector, <code>Date</code> variable</dd>
<dt>w</dt>
<dd>(optional) Numeric vector, weights of <code>y</code>. If not specified,
weights of all <code>NA</code> values will be <code>wmin</code>, the others will be 1.0.</dd>
<dt>type</dt>
<dd>integer, <code>1</code> or <code>-1</code><ul>
<li><code>1</code>: trough-to-trough curve fitting</li>
<li><code>-1</code>: peak-to-peak curve fitting</li>
</ul></dd>
<dt>e</dt>
<dd>The object returned by <code>init_param()</code></dd>
<dt>...</dt>
<dd>Others will be ignored.</dd></dl>

Arguments

init_param — init_param

<dl>

<dt>y</dt>
<dd>Numeric vector, vegetation index time-series</dd>


<dt>t</dt>
<dd>Numeric vector, <code>Date</code> variable</dd>


<dt>w</dt>
<dd>(optional) Numeric vector, weights of <code>y</code>. If not specified,
weights of all <code>NA</code> values will be <code>wmin</code>, the others will be 1.0.</dd>


<dt>type</dt>
<dd>integer, <code>1</code> or <code>-1</code><ul>
<li><code>1</code>: trough-to-trough curve fitting</li>
<li><code>-1</code>: peak-to-peak curve fitting</li>
</ul></dd>


<dt>e</dt>
<dd>The object returned by <code>init_param()</code></dd>


<dt>...</dt>
<dd>Others will be ignored.</dd>

</dl>

init_param: init_param

Description

Usage

Arguments

Examples