Qchart, TOS, Alchemchart data issues

Yesterday I posted something here concerning the RSI in TOS vs the RSI in Qcharts: [www.researchtrade.com]

Now today as I'm looking through it, I'm beginning to see that there are times, (often times) when the price data (OHLC) from the three charting services DO NOT match up.

There have been many many times when I will go to another data source, like Yahoo or google and even the nyse and s&p sites to compare the data. The majority of the time I find that Qcharts data is sometimes just plain WRONG, followed by Achemcharts while the TOS data seems to be right on point. It has happened so often in the past that I now just assume that TOS's data is correct and the other two are off. Sometimes way off. Also it seems that Qcharts and Alchemcharts share the same data source, although I have noticed slight differences once in a while.

I said all of that to say this. Since most all of the indicators plot their data points based on price, and price movements it's safe to assume that if you lines on the chart aren't matching of with other programs even after you have verified that they are setup the same way it can only come down to the price data being incorrect from one of the sources.

Apparently Qcharts isn't scrubbing their data very well at all, these days, followed by Alchemcharts while TOS's data seems to be the most on point of the 3. That has been my observation for quite some time now. Is there anyone else that sees it differently?

I was never very happy or impressed with the quality of QCharts data. I use TOS and TradeStation now and they seem to agree with very few exceptions when it comes to price and volume data.

One thing to watch out for is what price is used for the close. I use Schwab for brokerage functionality, but when using their scans to look at closing price I noticed that they equate last traded price with the closing price. If you have a stock that trades after hours this means the price continues to update after the market close. On a daily or higher time frame chart this will cause issues, particularly if there is significant price movement after regular trading hours. I cannot remember if QCharts had this issue, but I stopped using Schwab for end of day scans for "stocks that move" because of the way Schwab defines closing price.

I don't know who Alchemcharts uses to provide their data, but I seriously doubt they are getting it direct from the exchanges they cover. QCharts uses the eSignal data feed, so that should be pretty accurate. I know that TradeStation also has pretty accurate data.

One other data quality issue that drives me crazy is when you do scans that ask for NYSE stocks or NASDAQ stocks. TOS and TradeStation leave certain stocks off the list and in a few cases TOS assigns a stock to the wrong exchange. I have repeatedly asked TOS to clean this up and I get no response. To clean up my "stocks that move" end of day scans, I download CSV files of NYSE stocks and NASDAQ stocks from the NASDAQ web site and then use a data base matching program to scrub my data.

The bottom line is that there are no perfect data feeds for stock and option data, IMHO.