![]() ![]() In both cases, small degradations or dust deposition cause an optical reflectance loss. It is imperative to dissociate soiling that requires cleaning from irreversible degradations which affect the plant performance. The goal of this document is introducing these mathematical descriptions in a way easily to understand.ĭuring the life time of Concentrated Solar Power (CSP) plants, optical performance of solar mirrors is affected by soiling phenomena and surface degradation. However, these objects must be described mathematically when they are to be detected automatically with a computer. Scientists, engineers and medical doctors who intend to analyze images usually know how their images were generated and how the objects of interest look like. This document explains how digital images can be represented mathematically and basic methods for finding objects and describing regions. There are some basic methods to distinguish between objects and background and to describe regions in digital images. When processing an image with a computer, it must be digitized or created in a digital format. Images are generated by optical cameras, ultrasound, x-ray machines and other imaging devices. detection of surface defects in industrial quality control, detection of anatomical landmarks in surgery, counting cells in bio- technology and classification of regions in remote sensing. The only difference is the values displayed on the y-axis.There are various applications of image processing, e. Note that a frequency histogram and a relative frequency histogram will both look the exact same. For example, a shop might have a goal of selling 5% of their total items in the $41 – $50 price range.īy creating a relative frequency histogram of their data, they can see that they are meeting this goal: For example, a shop might have a goal to sell at least 10 items each week in the $41 – $50 range.īy creating a frequency histogram of their data, they can easily see that they’re not meeting their goal of selling 10 items per week in this price range:Ĭonversely, a relative frequency histogram is useful when you’re interested in percentage values. When to Use a Relative Frequency HistogramĪ frequency histogram can be useful when you’re interested in raw data values. ![]() Instead of displaying raw frequencies, a relative frequency histogram displays percentages. The only difference is the labels used on the y-axis. ![]() Similar to a frequency histogram, this type of histogram displays the classes along the x-axis of the graph and uses bars to represent the relative frequencies of each class along the y-axis. Once we have the relative frequency of each class, we can then create a relative frequency histogram to visualize these relative frequencies. We perform the same calculation for each class to get the relative frequencies. ![]() Thus, the relative frequency of the class $11 – $20 is 21 / 66 = 0.318. Next, there were 21 items sold in the price range of $11 – $20. Thus, the relative frequency of the class $1 – $10 is 20 / 66 = 0.303. Thus, we found the relative frequency of each class by taking the frequency of each class and dividing by the total items sold.įor example, there were 20 items sold in the price range of $1 – $10. The following table shows the relative frequencies of the same dataset we saw earlier: Item Price The following frequency histogram provides a visual representation of the frequency table above:Ī close cousin of a frequency table is a relative frequency table, which simply lists the frequencies of each class as a percentage of the whole. Often we use frequency histograms to visualize the values in a frequency table since it’s typically easier to gain an understanding of data when we can visualize the numbers.Ī histogram lists the classes along the x-axis of a graph and uses bars to represent the frequency of each class along the y-axis. In one column we have the “class” and in the other column we have the frequency of the class. This type of table is known as a frequency table. Frequencies simply tell us how many times a certain event has occurred.įor example, the following table shows how many items a particular shop sold in a week based on the price of the item: Item Price Often in statistics you will encounter tables that display information about frequencies. ![]()
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