# Principal Component Analysis: A Gap-Sharing Method

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A gap-filling method was developed based on the Principal Component Analysis (PCA) method. PCA is a widely used dimensionality reduction method to find a new set of variables as linear combinations of original variables, capturing most of the observed variance in the original data (Storch and Zwiers, 2002). It has been used in various climate studies for decomposing dominant mode (Storch and Zwiers, 2002) and time-series gap-filling (Beckers and Rixen, 2003; Kondrashov et al., 2014).
The algorithm developed for gap-filling in this study is described below: Step 1, initial guess For each station, its 50 nearest neighbors were selected. For each record with NoData, its neighbors having positive correlation with the station under examination
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At each time point, a T-test statistic is calculated by comparing the mean values before and after this time point. The maximum T-test statistic value and the time is picked up. Then the probability of observing a maximum T-test statistic less than the observed maximum T-test value in a randomly drawn time series is calculated using an approximation function generated from Monte-Carlo experimentation. If the probability is greater than a given criteria (PROB), the time series are split at this time point. The BGHS method will further process each sub time series until the length of the sub time series is less than a given length (MIN_LEN). When working on a sub time series, additional T-tests (ALPHA) would be conducted at a proposed splitting time point, comparing the separated sub time series with its former and latter neighboring sub time series separated in previous recursion. If any of the T-tests were not significant, the proposed split would be rejected. The BGHS method can be used to split non-stationary time series, and the formulation of its statistical test assures it is stricter than other T-test based change detection method, for example, moving window T-test. It has been widely used to analyze biophysical and physiological data (Fukuda et al., 2004), financial time series (Tóth et al., 2010), and geophysical time series (Feng et al., …show more content…
The results suggest 1976 / 1977 as the break year for air temperature in CA, with 113 out of 369 stations having statistically significant shift of mean annual temperature in the 1970s, and 69 stations witnessed such a change during 1976 / 1977 (Figure 6-1). Distribution of stations with significant break of mean air temperature do not have specific spatial patterns. At the same time, there does not exist a general break year for precipitation (Figure 6-2). As a result, the research period was cut into two sub periods in the year 1976 /

• ## Elekta Synergy S Linear Accelerator Lab Analysis

This minimizes the linac dose rate fluctuation which is the same function performed by the reference detector. The pause time was determined by comparing the profiles obtained from two detector method and the single detector method to optimize both the beam on time and the noise. The single detector mode is further optimized by utilizing two algorithms that are within the Omnipro software. The gradient algorithm is used in measuring beam profiles as the detector’s step sizes alter if two positions have a difference that is more than predicted. The breakpoint algorithm was used for PDD measurements, as the algorithm changed the step sizes after a certain depth was reached.…

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• ## Sp2750 Experiment 4

-We want to prevent anticipation error. When the fore-period remains the same, there will be a learning effect by performers and they may be able to anticipant the appearance of the signal. As a result, the measured RT will be shorter than the real RT. (iv) Why was randomization necessary from Task 1b…

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• ## Civil Military Cooperation In Disaster Aid Case Study

Validity Testing. Before using the questionnaire to collect the data, the validity to the respondent must firstly be tested by using correlation technique "Product Moment" against each item statement/question on the research instrument with Karl Pearson coefficient formula. Validity coefficient is significant if r output > 0 and each item question/statement in the instrument is valid if routput > rtable. b. Reliability Testing.…

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• ## Serial Correlation Essay

We will refer to n as our sample size for each run. The MSER technique used various truncation values (d*), minimizing standard error, for each of the 10 runs. The resultant point estimates are independent, but based on various sizes of n. To prevent introducing bias into our results, we weighted each estimate by n. A histogram was generated using x ̅, weighted by n, seen in Figure 7. Note that our standard deviation was extremely high. To minimize the variance of our mean, we calculated a new weighted average (w), using the following formula: N denotes the total number of simulation runs; in this case, N = 10.…

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• ## Excel Diagnostic Services

Thus, it is probably a good idea to bring the slotter process under control and then work on improving performance. An issue that arises is the evaluation of control limits for the future because the current control limits were evaluated using two points that are out of control. One option is to simply delete the out of control points and recalculate the control limits to be used in the future. In the case of the slotter, we would delete the entries for 6/6/99 and 6/21/99 and repeat the above evaluation to obtain new control…

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• ## Analysis Of The RARMA Model

One can see that the peak of the distribution for all channels has come closer to zero after applying the RARMA algorithm. This figure should be accompanied with Table 2, which tabulates the resulting mean radiance departures before and after applying the radiometric adjustment procedure. Computed biases seem to vary from one channel to another, which is to be expected. Up to ~5 K bias is observed in some channels, more specifically in channels 3 and 4 (18 GHz). Nevertheless, after applying the RARMA algorithm, a significant bias reduction has been possible.…

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• ## PICT Case Study

Then, the result will be sorted according to the weight of each pairs. Considered general PROW algorithm while ignoring the pre and post PROW algorithm. The complexity of PROW algorithm can be calculated as O(n) for while statement in line 2 since it iterate until specified value is meet. Then, in for loop the maximum number is when no more remaining pair is found, n. Since the second for loop also have same maximum number, Big-O notation for this for loop is O(n2). Thus, the lower bound and final result of Big-O notation is…

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• ## Reference Evapotranspiration And Climate Change

(2007) pioneered a technique for attributing the change of evaporative demand through a full mathematical based formulation of pan evaporation. This mathematical approach has been commonly used to attribute the relative change in pan evaporation (Liu and McVicar 2012; Wang et al. 2015) but is occasionally used for ETref changes analysis. For instance, Li et al. (2016); Liu and Zhang (2013) used this technique appropriately for an attribution…

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• ## Trial And Incongruency Effect

To equalize the number of congruent and incongruent trials, Ullsperger et al. (2005) created randomized trial sets from a pool that consisted of each possible incongruent combination once and each possible congruent trial eight times, for a total of 72 combinations for each trial type. Each trial was preceded by a 50-msec warning tone and a 1,000-msec preparatory period. The time between a participant’s response and the beginning of a new trial varied randomly from 3,500 to 5,500 msec. In order to test their hypothesis and evaluate whether conflict adaptation was present, Ullsperger et al.…

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• ## Essay On ADI Strategy In Mid-80's

Ans. Half-Life: The half-life dynamic is the interactive learning loop through TQM; over a consistent time interval each process can reduce up to 50%. The improvement team needs to discover the basis reason of defects recognized, primarily based on importance rank them, later propos, and design. Then test and enforce solutions using PDA. Every process had its own unique rate, which can be found using the slope of the line fit which to the data.…

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