opencv convertTo 好像是用round

from here

When the parameter is a floating-point value and the target type is an integer (8-, 16- or 32-bit), the floating-point value is first rounded to the nearest integer and then clipped if needed (when the target type is 8- or 16-bit).


one metric

好吧,好好想想ipcamsum和good hearing目前应该focus的metric
ipcamsum主要有两个metric:setup rate和retention rate。这两个都还不好。目前应该focus在retention rate。可以做的事情:email daily/weekly summary,mobile app,另外,得用上flurry。

good hearing。long term retention rate也不是很高。也许应该找一找有hearing loss的老年人。让他们评价评价。在app里面加入反馈机制?

lean analytics quotes

Don’t sell what you can make; make what you can sell.

Lean Analytics is used to measure that progress, helping you to ask the most important questions and get clear answers quickly.

We’re all delusional — some more than others. Entrepreneurs are the most delusional of all.

Your delusions, no matter how convincing, will wither under the harsh light of data.

You need to lie to yourself, but not to the point where you’re jeopardizing your business. That’s where data comes in.

Instincts are experiments. Data is proof.

Management guru and author Peter Drucker famously observed, “If you can’t measure it, you can’t manage it.”

A Concierge MVP won’t scale, but it’s fast and easy in the short term.

A concierge approach in which you run things behind the scenes for the first few customers lets you check whether the need is real; it also helps you understand which things people really use and refine your process before writing a line of code or hiring a single employee.

The key metric Airbnb tracked was shoots per month, because it had already proven with its Concierge MVP that more professional photographs meant more bookings.

Lean, analytical thinking is about asking the right questions, and focusing on the one key metric that will produce the change you’re after.

In a startup, the purpose of analytics is to find your way to the right product and market before the money runs out.

A good metric is comparative. Being able to compare a metric to other time periods, groups of users, or competitors helps you understand which way things are moving. “Increased conversion from last week” is more meaningful than “2% conversion.”

A good metric is understandable.

A good metric is a ratio or a rate.

Ratios are easier to act on.

Ratios are inherently comparative.

Ratios are also good for comparing factors that are somehow opposed, or for which there’s an inherent tension.

A good metric changes the way you behave. This is by far the most important criterion for a metric: what will you do differently based on changes in the metric?

Drawing a line in the sand is a great way to enforce a disciplined approach. A good metric changes the way you behave precisely because it’s aligned to your goals of keeping users, encouraging word of mouth, acquiring customers efficiently, or generating revenue.

If you measure something and it’s not attached to a goal, in turn changing your behavior, you’re wasting your time.

Analysts look at specific metrics that drive the business, called key performance indicators (KPIs). Every industry has KPIs — if you’re a restaurant owner, it’s the number of covers (tables) in a night; if you’re an investor, it’s the return on an investment; if you’re a media website, it’s ad clicks; and so on.

If quantitative data answers “what” and “how much,” qualitative data answers “why.” Quantitative data abhors emotion; qualitative data marinates in it.

If you have a piece of data on which you cannot act, it’s a vanity metric.

Whenever you look at a metric, ask yourself, “What will I do differently based on this information?” If you can’t answer that question, you probably shouldn’t worry about the metric too much.

And if you don’t know which metrics would change your organization’s behavior, you aren’t being data-driven. You’re floundering in data quicksand.

The real metric of interest — the actionable one — is “percent of users who are active.” This is a critical metric because it tells us about the level of engagement your users have with your product.

When you change something about the product, this metric should change, and if you change it in a good way, it should go up. That means you can experiment, learn, and iterate with it.

Another interesting metric to look at is “number of users acquired over a specific time period.”

There’s a “critical mass” of engagement necessary for any community to take off. Mild success may not give you escape velocity. As a result, it’s better to have fervent engagement with a smaller, more easily addressable target market. Virality requires focus.

finding the cause of something means you can change it.

correlation is good. Causality is great. Sometimes, you may have to settle for the former — but you should always be trying to discover the latter.

First, know your customer. There’s no substitute for engaging with customers and users directly. All the numbers in the world can’t explain why something is happening. Pick up the phone right now and call a customer, even one who’s disengaged.

Testing is at the heart of Lean Analytics. Testing usually involves comparing two things against each other through segmentation, cohort analysis, or A/B testing.

Bud Caddell has three clear criteria for deciding what to spend your time on: something that you’re good at, that you want to do, and that you can make money doing.

using data to optimize one part of your business, without stepping back and looking at the big picture, can be dangerous — even fatal.

change favors local maxima; innovation favors global disruption.

Lean Startup is focused on learning above everything else, and encourages broad thinking, exploration, and experimentation. It’s not about mindlessly going through the motions of build > measure > learn — it’s about really understanding what’s going on and being open to new possibilities.

We sometimes remind early-stage founders that, in many ways, they aren’t building a product. They’re building a tool to learn what product to build. This helps separate the task at hand — finding a sustainable business model — from the screens, lines of code, and mailing lists they’ve carefully built along the way.

The fundamental KPI for stickiness is customer retention.

The question this poses a of course, is how do you know if you’ve achieved product/market fit? Sean devised a simple survey that you can send customers (available at to determine if you’re ready for accelerated growth. The most important question in the survey is “How would you feel if you could no longer use this product or service?” In Sean’s experience, if 40% of people (or more) say they’d be very disappointed to lose the service, you’ve found a fit, and now it’s time to scale.

one of the keys to startup success is achieving real focus and having the discipline to maintain it.

If there’s any secret to success for a startup, it’s focus.

at any given time, there’s one metric you should care about above all else. Boiled down to its very essence, Lean Startup is really about getting you to focus on the right thing, at the right time, with the right mindset.

In the world of analytics and data, this means picking a single metric that’s incredibly important for the step you’re currently working through in your startup. We call this the One Metric That Matters (OMTM).

Capture everything, but focus on what’s important.

having company-wide transparency into the metrics keeps us all informed, and is a great reminder of the progress (as well as the challenges) we are seeing as a company.”

While it’s great to track many metrics, it’s also a sure way to lose focus. Picking a minimal set of KPIs on which your business assumptions rely is the best way to get the entire organization moving in the same direction.

Picking the OMTM lets you run more controlled experiments quickly and compare the results more effectively.

It’s critical to move through the build → measure → learn cycle as quickly and as frequently as possible.

In the long term, the riskiest part of a business is often directly tied to how it makes money.

When you reduce things to their basic building blocks in this way, you come up with only a few fundamental business models on the Web. Interestingly, all of them share some common themes. First, their aim is to grow (in fact, Paul Graham says that a focus on growth is the one defining attribute of a startup).[ 21 ] And second, that growth is achieved by one of Eric Ries’s fundamental Engines of Growth: an increase in stickiness, virality, or revenue.

Sergio Zyman, Coca-Cola’s CMO, said marketing is about selling more stuff to more people more often for more money more efficiently.

Early on, stickiness tends to be a key knob on which to focus, because until your core early adopters find your product superb, it’s unlikely you can achieve good viral marketing.

You need to segment real, valuable users from drive-by, curious, or detrimental ones. Then you need to make changes that maximize the real users and weed out the bad ones.

Not all customers are good. Don’t fall victim to customer counting. Instead, optimize for good customers and segment your activities based on the kinds of customer those activities attract.

Freemium isn’t a business model — it’s a marketing tactic. SaaS isn’t a business model — it’s a way of delivering software. The ads on a media site aren’t a business model — they’re a way of collecting revenue.



这两天看lean analytics。觉得受益颇多。假如应用到一个中文学校的话。。。

首先是OMTM,one metric that matters。就是在任何阶段,有一个唯一的metric用来衡量performance的好坏。也用来作为所有人员共同努力的方向。比如在某个阶段,profit最重要。那么就maximize profit。如果revenue/cost稳定了,足够survive了,也许开始要考虑scale。扩张规模。这个时候,可以拿head count来作为metric。学生人数越多越好。所有管理者,工作人员,包括老师,都尽量增加学生人数。这个时候,就不要minimize cost。这个阶段的主要任务是占领市场,扩大影响。如果影响够大了,有足够多的人来报名了。但是第二个学期他们很多都不来了,也许因为老师不好,也许因为课程设置不好。这个时候,就应该拿retention rate作为metric。尽量减少流失率。












看看下一代nexus 7的摄像头如何

准备拿这个平板做测试工具了,暑假让intern把good hearing的app port到android平台






第二个是代码重构一下,加入些东西,主要是给用户提供更多的反馈,比如daily summary, monthly summary,注册和设置反馈,这样可以提高黏性。另外,搞个mobile app,就基于html5,把notification弄进去。

第三是更好的tracking和statistics,自动生成一些指标的report。光靠google analytics不够。必须得写些程序。


第五是zoom in。只针对foscam或者类似camera的用户。这样setup可能更简单。

第六是搞个论坛,blog, wiki。建立起社区。


感觉搞这个东西看起来容易,其实做成功很难。不如搞mobile app。商业模式比较简单,用户也容易弄一些。