John Snow was once a well-known doctor in London. He had excellent medical skills, so that Queen Victoria fired him as her private doctor. Cholera was a deadly disease at the time, people did not know its cause, nor understand its treatment. There were two views of cholera causes: The first view is the cholera virus breeding, it was like a surge of dangerous gases float around in the air, until the victims of the virus found. The second view is that people eat when the virus into the body. Virus attack from the stomach rapidly bring disaster to the whole body, the patient will die soon.
John Snow speculated that the second statement was correct, but he needed evidence. Thus in the 1854, London cholera outbreak again when he was preparing for his investigations. When the rapid spread of cholera in the slums, he began to collect data in two specific streets. The cholera epidemic was very serious, resulting in more than 500 people died within 10 days. He determined to identify the reason.
First, he marked on a map the exact place where all the dead live. This provided him with a description of cholera causes valuable clues. Many of the dead are near the water pump in Broad Street (especially the street, 16,37,38 and 40). John Snow also noted that some of the residents (such as the width of the street, No. 20 and No. 21, Cambridge street No. 8 and No. 9) had bare death. He did not expect it and he made a further investigation. He found that these people are working in Cambridge Street on the 7th of pubs and taverns to provide them with free beer, so they do not have to drink the water pump pumped water. Cholera epidemic seems to be blamed on the drinking water.
Second, John Snow investigated the water resource of these two streets. He found that water is calling from the river, and the river was in London the dirty water pollution discharge. John Snow immediately called wide panic of the people in the streets removed the pump handle. In this way, water pumps could not be used. Soon, the epidemic has been alleviated. The map contains —the street names, breweries, workhouses, and water pumps—the map revealed an overwhelming connection between the Broad Street pump and cholera transmission. However, what we can’t see from John’s map, it is time. After the handle was removed, there are still people dead because it was too late. If we use different sized points represent different month, the death can be visualized better.
Before this map, John Snow created a map during his South London study that featured handinked dots, which were hard to read, and cloudy colors that tried, but failed to show the connection between cholera deaths and water sources. Snow also published a table to tell the same story. But it wasn’t quite right. It lacked key pieces of information gleaned. After these failures, Snow realized to tell the truth of data, he needed to make some variables and their connections visualized.
The cholera outbreak in London tells us sometimes visualization is better than calculation. Data visualization is presenting the fact into maps or other tools. Map, the ground coordinates information visualization and generates graphical tools, it is easier for people to explore the relationship of them, then discover hidden truths. Let’s zoom out. Any thing or fact is one type of information: tables, graphics, maps, and even text, whether static or dynamic, and provide us with a means of understanding the world. Visualization will be several times to enlarge their power.
Visuanalyze 